John Colford Jr. MD, PhD, MPH

• Professor, Epidemiology

https://publichealth.berkeley.edu/people/john-colford/

However androgen hormone jinteli purchase proscar 5 mg visa, the roots o the short mesenteries do not arise rom the midline but shit to the let or right by a usion process like that described or the descending colon prostate-7 review purchase proscar us. A mesentery connects an intraperitoneal organ to the body wall-usually the posterior abdominal wall androgen hormone and pregnancy generic proscar 5 mg with amex. The small intestine mesentery is usually reerred to simply as "the mesentery"; however prostate cancer hematuria generic proscar 5mg without prescription, mesenteries related to other specic parts o the alimentary tract are named accordingly-or example prostate cancer family history purchase 5mg proscar free shipping, the transverse and sigmoid mesocolons mens health 8 week program cheap proscar line. Mesenteries have a core o connective tissue containing blood and lymphatic vessels, nerves, lymph nodes, and at. An omentum is a double-layered extension or old o peritoneum that passes rom the stomach and proximal part o the duodenum to adjacent organs in the abdominal cavity. The greater omentum is a prominent, our-layered peritoneal old that hangs down like an apron rom the greater curvature o the stomach and the proximal part o the duodenum. Ater descending, it olds back and attaches to the anterior surace o the transverse colon and its mesentery. The lesser omentum is a much smaller, double-layered peritoneal old that connects the lesser curvature o the stomach and the proximal part o the duodenum to the liver. It also connects the stomach to a triad o structures that run between the duodenum and liver in the ree edge o the lesser omentum. The hepatogastric and hepatoduodenal ligaments are continuous parts o the lesser omentum and are separated only or descriptive convenience. The stomach is connected to the: inerior surace o the diaphragm by the gastrophrenic ligament. All these structures have a continuous attachment along the greater curvature o the stomach and are all part o the greater omentum, separated only or descriptive purposes. Some o the acts relating to this include the ollowing: the peritoneal cavity houses a great length o gut, most o which is covered with peritoneum. Extensive continuities are required between the parietal and visceral peritoneum to convey the necessary neurovascular structures rom the body wall to the viscera. Various terms are used to describe the parts o the peritoneum that connect organs with other organs, or to the abdominal wall, and the compartments and recesses that are ormed as a consequence. A mesentery is a double layer o peritoneum that occurs as a result o the invagination o the peritoneum by an organ and constitutes a continuity o the visceral and parietal peritoneum. In this opened peritoneal cavity, parts o the greater omentum, transverse colon, and the small intestine and its mesentery have been cut away to reveal deep structures and the layers o the mesenteric structures. The mesentery o the jejunum and ileum (small intestine) and sigmoid mesocolon have been cut close to their parietal attachments. The greater omentum is shown in its "normal" position, covering most o the abdominal viscera. The lesser omentum, attaching the liver to the lesser curvature o the stomach, is shown by reecting the liver and gallbladder superiorly. The greater omentum has been removed rom the greater curvature o the stomach and transverse colon to reveal the intestines. The greater omentum has been reected superiorly, and the small intestine has been retracted to the right side to reveal the mesentery o the small intestine and the transverse mesocolon. Although intraperitoneal organs may be almost entirely covered with visceral peritoneum, every organ must have an area that is not covered to allow the entrance or exit o neurovascular structures. Such areas are called bare areas, ormed in relation to the attachments o the peritoneal ormations to the organs, including mesenteries, omenta, and ligaments that convey the neurovascular structures. A peritoneal old is a refection o peritoneum that is raised rom the body wall by underlying blood vessels, ducts, and ligaments ormed by obliterated etal vessels. Some peritoneal olds contain blood vessels and bleed i cut, such as the lateral umbilical olds, which contain the inerior epigastric arteries. A peritoneal recess, or peritoneal ossa, is a pouch o peritoneum that is ormed by a peritoneal old. The central part o the greater omentum has been cut out to show its relation to the transverse colon and mesocolon. The term greater omentum is oten used as a synonym or the gastrocolic ligament, but it actually also includes the gastrosplenic and gastrophrenic ligaments, all o which have a continuous attachment to the greater curvature o the stomach. The hepatoduodenal ligament (ree edge o lesser omentum) conveys the portal triad: hepatic artery, bile duct, and portal vein. Subdivisions o Peritoneal Cavity Ater the rotation and development o the greater curvature o the stomach during development (see the Clinical Box "Brie Review o Embryological Rotation o Midgut," p. A surgical incision through the anterolateral abdominal wall enters the greater sac. The transverse mesocolon (mesentery o the transverse colon) divides the abdominal cavity into a supracolic compartment, containing the stomach, liver, and spleen, and an inracolic compartment, containing the small intestine and ascending and descending colon. The inracolic compartment lies posterior to the greater omentum and is divided into right and let inracolic spaces by the mesentery o the small intestine. Free communication occurs between the supracolic and the inracolic compartments through the paracolic gutters, the grooves between the lateral aspect o the ascending or descending colon and the posterolateral abdominal wall. The omental bursa is an extensive sac-like cavity that lies posterior to the stomach, lesser omentum, and adjacent structures. The omental bursa has a superior recess, limited superiorly by the diaphragm and the posterior layers o the coronary ligament o the liver, and an inerior recess between the superior parts o the layers o the greater omentum. The omental bursa permits ree movement o the stomach on the structures posterior and inerior to it because the anterior and posterior walls o the omental bursa slide smoothly over each other. Most o the inerior recess o the bursa becomes sealed o rom the main part posterior to the stomach ater adhesion o the anterior and posterior layers o the greater omentum. The omental bursa communicates with the greater sac through the omental oramen (epiploic oramen), an opening situated posterior to the ree edge o the lesser omentum (hepatoduodenal ligament). This median section o the abdominopelvic cavity shows the subdivisions o the peritoneal cavity. The supracolic and inracolic compartments o the greater sac are shown ater removal o the greater omentum. The inracolic spaces and paracolic gutters determine the ow o ascitic uid (arrows) when inclined or upright. The boundaries o the omental oramen are as ollows: Anteriorly: the hepatoduodenal ligament (ree edge o lesser omentum), containing the hepatic portal vein, hepatic artery, and bile duct. This section shows that the omental bursa is an isolated part o the peritoneal cavity, lying dorsal to the stomach and extending superiorly to the liver and diaphragm (superior recess) and ineriorly between the layers o the greater omentum (inerior recess). The red arrows pass rom the greater sac through the omental oramen into the omental bursa. The index fnger is passing rom the greater sac through the omental oramen into the omental bursa (lesser sac). The hepatoduodenal ligament is being pinched between thumb and index fnger, which would compress the structures o the portal triad (portal vein, hepatic artery, and bile duct). A primary mechanism in preventing such inection is a mucous plug that eectively blocks the external os (opening) o the uterus to most pathogens, but not to sperm cells. It is the covering o visceral peritoneum (oten reerred to clinically as the serosa) that makes watertight end-to-end anastomoses o intraperitoneal organs, such as the small intestine, relatively easy to achieve. It is more dicult to achieve watertight anastomoses o extraperitoneal structures that have an outer adventitial layer, such as the thoracic esophagus. Because o the high incidence o complications such as peritonitis and adhesions (see the Clinical Box "Peritoneal Adhesions and Adhesiotomy," p. When opening the peritoneal cavity is necessary, great eort is made to avoid contamination o the cavity. The Peritoneum and Surgical Procedures Because the peritoneum is well innervated, patients undergoing abdominal surgery experience more pain with large, invasive, open incisions o Peritonitis and Ascites When bacterial contamination occurs during laparotomy, or when the gut is traumatically penetrated or ruptured as the result o inection and infammation. Given the extent o the peritoneal suraces and the rapid absorption o material, including bacterial toxins, rom the peritoneal cavity, when a peritonitis becomes generalized (widespread in the peritoneal cavity), the condition is dangerous and perhaps lethal. In addition to the severe abdominal pain, tenderness, nausea and/or vomiting, ever, and constipation are present. General peritonitis also occurs when an ulcer perorates the wall o the stomach or duodenum, spilling its acidic contents into the peritoneal cavity. Ascites may also occur as a result o mechanical injury (which may also produce internal bleeding) or other pathological conditions, such as portal hypertension (venous congestion), widespread metastasis o cancer cells to the abdominal viscera, and starvation (when plasma proteins ail to be produced, altering concentration gradients and producing a paradoxically protuberant abdomen). In all these cases, the peritoneal cavity may be distended with several liters o abnormal fuid, interering with movements o the viscera. Rhythmic movements o the anterolateral abdominal wall normally accompany respirations. I the abdomen is drawn in as the chest expands (paradoxical abdominothoracic rhythm) and muscle rigidity is present, either peritonitis or pneumonitis (infammation o the lungs) may be present. Because the intense pain worsens with movement, people with peritonitis commonly lie with their knees fexed to relax their anterolateral abdominal muscles. Abdominal Paracentesis Most cases o peritonitis are secondary, having a surgical cause. In rare cases, individuals with chronic ascites rom a condition such as cirrhosis will develop primary peritonitis in which the ascites becomes inected without a surgical cause. Treatment o generalized peritonitis includes removal o the ascitic fuid, or relie when large amounts are present, and diagnosis. Occasionally, more localized accumulations o fuid may have to be removed or analysis. Surgical puncture o the peritoneal cavity or the aspiration or drainage o fuid is called paracentesis. The needle is inserted superior to the empty urinary bladder, in a location that avoids the inerior epigastric artery. Peritoneal Dialysis the peritoneum is a semipermeable membrane with an extensive surace area, much o which (subdiaphragmatic portions in particular) overlies blood and lymphatic capillary beds. In renal ailure, waste products such as urea accumulate in the blood and tissues and ultimately reach atal levels. Peritoneal dialysis may be perormed in which soluble substances and excess water are removed rom the system by transer across the peritoneum, using a dilute sterile solution that is introduced into the peritoneal cavity on one side and then drained rom the other side. Diusible solutes and water are transerred between the blood and the peritoneal cavity as a result o concentration gradients between the two fuid compartments. For the long term, it is preerable to use direct blood fow through a renal dialysis machine. Peritoneal Adhesions and Adhesiotomy I the peritoneum is damaged, by a stab wound, or example, or inected, the peritoneal suraces become infamed, making them sticky with brin. As healing occurs, the brin may be replaced with brous tissue, orming abnormal attachments between the visceral peritoneum o adjacent viscera, or between the visceral peritoneum o an organ and the parietal peritoneum o the adjacent abdominal wall. This tethering may cause chronic pain or emergency complications such as intestinal obstruction when the intestine becomes twisted around an adhesion (volvulus). Functions o Greater Omentum the greater omentum, large and at-laden, prevents the visceral peritoneum rom adhering to the parietal peritoneum. It has considerable mobility and moves around the peritoneal cavity with peristaltic movements o the viscera. It oten orms adhesions adjacent to an infamed organ, such as the appendix, sometimes walling it o and thereby protecting other viscera rom it. Thus, it is common when entering the abdominal cavity, in either dissection or surgery, to nd the omentum markedly displaced rom the "normal" position in which it is almost always depicted in anatomical illustrations. The greater omentum also cushions the abdominal organs against injury and orms insulation against loss o body heat. The abscess may be walled ineriorly by adhesions o the greater omentum (see the Clinical Box "Subphrenic Abscesses," p. Fluid in Omental Bursa Peroration o the posterior wall o the stomach results in the passage o its fuid contents into the omental bursa. An infamed or injured pancreas can also result in the passage o pancreatic fuid into the bursa, orming a pancreatic pseudocyst. Spread o Pathological Fluids Peritoneal recesses are o clinical importance in connection with the spread o pathological fuids such as pus, a product o infammation. The recesses determine the extent and direction o the spread o fuids that may enter the peritoneal cavity when an organ is diseased or injured. Internal Hernia Through Omental Foramen Although uncommon, a loop o small intestine may pass through the omental oramen into the omental bursa and be strangulated by the edges o the oramen. As none o the boundaries o the oramen can be incised because each contains blood vessels, the swollen intestine must be decompressed using a needle so it can be returned to the greater sac o the peritoneal cavity through the omental oramen. Flow o Ascitic Fluid and Pus the paracolic gutters are o clinical importance because they provide pathways or the fow o ascitic fuid and the spread o intraperitoneal inections. Purulent material (consisting o or containing pus) in the abdomen can be transported along the paracolic gutters into the pelvis, especially when the person is upright. Conversely, inections in the pelvis may extend superiorly to a subphrenic recess situated under the diaphragm (see the Clinical Box "Subphrenic Abscesses," p. Temporary Control o Hemorrhage rom Cystic Artery the cystic artery must be ligated or clamped and then severed during cholecystectomy, removal o the gallbladder. Sometimes, however, the artery is accidentally severed beore it has been adequately ligated. The surgeon can control the hemorrhage by compressing the hepatic artery as it traverses the hepatoduodenal ligament. The index nger is placed in the omental oramen and the thumb on its anterior wall. Alternate compression and release o pressure on the hepatic artery allows the surgeon to identiy the bleeding artery and clamp it. This is also done sometimes to provide temporary control during cases o severe trauma to the liver or associated structures ("Pringle maneuver").

Diseases

• Purpura, Sch?nlein Henoch
• Polymyalgia rheumatica
• Procarcinoma
• Ehlers Danlos syndrome
• Radio digito facial dysplasia
• Lipogranulomatosis
• D ercole syndrome
• Sclerocornea, syndactyly, ambiguous genitalia

Also involved in the loss or retention o body heat are the small arteries (arterioles) within the dermis prostate cancer 8k discount proscar 5 mg amex. They dilate to ll supercial capillary beds to radiate heat (skin appears red) or constrict to minimize surace heat loss (skin prostate exam procedure video discount proscar generic, especially o the lips and ngertips prostate cancer xofigo trusted proscar 5 mg, appears blue) mens health 2010 buy cheap proscar 5mg line. Other skin structures or derivatives include the nails (ngernails prostate infection treatment buy proscar with paypal, toenails) mens health december 2015 order proscar with a mastercard, the mammary glands, and the enamel o teeth. Located between the overlying skin (dermis) and underlying deep ascia, the subcutaneous tissue (supercial ascia) is composed mostly o loose connective tissue and stored at and contains sweat glands, supercial blood vessels, lymphatic vessels, and cutaneous nerves. The neurovascular structures o the integument (cutaneous nerves, supercial vessels) course in the subcutaneous tissue, distributing only their terminal branches to the skin. In addition, the distribution o subcutaneous tissue varies considerably in dierent sites in the same 1 An incision made across the cleavage lines is more likely to gape, increasing healing time, and result in increased scar tissue. An incision made parallel to the cleavage lines results in less gaping, faster healing, and less scar tissue. The dashed lines indicate the predominant direction o the collagen fbers in the dermis. Long, relatively sparse skin ligaments allow the mobility o the skin demonstrated in part A. The skin o the palm (like that o the sole) is frmly attached to the underlying deep ascia. Compare, or example, the relative abundance o subcutaneous tissue evident by the thickness o the old o skin that can be pinched at the waist or thighs with the anteromedial part o the leg (the shin, the anterior border o the tibia) or the back o the hand, the latter two being nearly devoid o subcutaneous tissue. Also consider the distribution o subcutaneous tissue and at between the sexes: In mature emales, it tends to accumulate in the breasts and thighs, whereas in males, subcutaneous at accumulates especially in the lower abdominal wall. It also provides padding that protects the skin rom compression by bony prominences, such as those in the buttocks. The length and density o these ligaments determines the mobility o the skin over deep structures. Where skin ligaments are longer and sparse, the skin is more mobile, such as on the back o the hand. Where ligaments are short and abundant, the skin is rmly attached to the underlying deep ascia, such as in the palms and soles. The skin ligaments are long but particularly well developed in the breasts, where they orm weight-bearing suspensory ligaments (see Chapter 4, Thorax). When the blood is not carrying enough oxygen rom the lungs, such as in a person who has stopped breathing or whose circulation is unable to send adequate amount o blood through the lungs, the skin can appear bluish (cyanotic). Cyanosis occurs because the oxygen-carrying hemoglobin o blood appears bright red when carrying oxygen (as it does in arteries and usually does in capillaries) and appears deep, purplish blue when depleted o oxygen, as it does in veins. Cyanosis is especially evident where skin is thin, such as the lips, eyelids, and deep to the transparent nails. Skin injury, exposure to excess heat, inection, infammation, or allergic reactions may cause the supercial capillary beds to Integumentary System 15 become engorged, making the skin look abnormally red, a sign called erythema. In certain liver disorders, a yellow pigment called bilirubin builds up in the blood, giving a yellow appearance to the whites o the eyes and skin, a condition called jaundice. Skin color changes are most readily observed in people with light-colored skin and may be dicult to discern in people with dark skin. Stretch marks generally ade ater pregnancy and weight loss, but they never disappear completely. Supercial lacerations penetrate the epidermis and perhaps the supercial layer o the dermis; they bleed but do not interrupt the continuity o the dermis. Deep lacerations penetrate the deep layer o the dermis, extending into the subcutaneous tissue or beyond; they gape and require approximation o the cut edges o the dermis (by suturing, or stitches) to minimize scarring. Burns are classied, in increasing order o severity, based on the depth o skin injury and the need or surgical intervention. The current classication system does not use numerical designations except or ourth-degree burns (the most severe). In general, lacerations or incisions that parallel the tension lines usually heal well with little scarring because there is minimal disruption o collagen bers. However, a laceration or incision across the tension lines disrupts more collagen bers. When other considerations, such as adequate exposure and access or avoidance o nerves, are not o greater importance, surgeons attempting to minimize scarring or cosmetic reasons may use surgical incisions that parallel the tension lines. Stretch Marks in Skin the collagen and elastic bers in the dermis orm a tough, fexible meshwork o tissue. However, marked and relatively ast size increases, such as the abdominal enlargement and weight gain accompanying pregnancy, can stretch the skin too much, damaging the collagen bers in the dermis. Partial-thickness burn: epidermis and supercial dermis are damaged with blistering (supercial partial thickness) or loss (deep partial thickness); nerve endings are damaged, making this variety the most painul; except or their most supercial parts, the sweat glands and hair ollicles are not damaged and can provide the source o replacement cells or the basal layer o the epidermis along with cells rom the edges o the wound; healing occurs slowly (3 weeks to several months), leaving scarring and some contracture, but it is usually complete. Full-thickness burn: the entire thickness o the skin is damaged and oten the subcutaneous tissue; there is marked edema and the burned area is numb since sensory endings are destroyed; minor degree o healing may occur at the edges, but the open, ulcerated portions require skin grating: dead material (eschar) is removed and replaced (grated) over the burned area with skin harvested (taken) rom a nonburned location (autograt) or using skin rom human cadavers or pigs or cultured or articial skin. Burns are classied as severe i they cover 20% or more o the total body surace area (excluding supercial burns like sunburn), are complicated by trauma or inhalation injury, or are caused by chemicals or high-voltage electricity. One way to estimate the surace area aected by a burn in an adult is to apply the "rule o nines," in which the body is divided into areas that are approximately 9% or multiples o 9% o the total body surace. Three actors that increase the risk o death rom burn injury are (1) age older than 60 years, (2) partial-thickness and ull-thickness burns o over 40% body surace area, and (3) the presence o inhalation injury. Anterior and posterior head and neck 9% Anterior and posterior arms, for forearms, and ha hands 18 18% 4. Underlying the subcutaneous tissue (supercial ascia) almost everywhere is the deep ascia. The deep ascia is a dense, organized connective tissue layer, devoid o at, that covers most o the body parallel to (deep to) the skin and subcutaneous tissue. Extensions rom its internal surace invest deeper structures, such as individual muscles (when it may also be called epimysium-see. In the limbs, groups o muscles with similar unctions, usually sharing the same nerve supply, are located in ascial compartments. These compartments are separated by thick sheets o deep ascia, called intermuscular septa, that extend centrally rom the surrounding ascial sleeve to attach to bones. In a ew places, the deep ascia gives attachment (origin) to the underlying muscles (although it is not usually included in lists or tables o origins and insertions); but in most places, the muscles are ree to contract and glide deep to it. However, the deep ascia itsel never passes reely over bone; where deep ascia contacts bone, it blends rmly with the periosteum (bone covering). The relatively unyielding deep ascia investing muscles, and especially that surrounding the ascial compartments in the limbs, limits the outward expansion o the bellies o contracting skeletal muscles. Blood is thus pushed out as the veins o the muscles and compartments are compressed. Valves within the veins allow the blood to fow only in one direction (toward the heart), preventing the backfow that might occur as the muscles relax. Thus, deep ascia, contracting muscles, and venous valves work together as a musculovenous pump to return blood to the heart, especially in the lower limbs where blood must move against the pull o gravity. Subserous ascia, with varying amounts o atty tissue, lies between the internal suraces o the musculoskeletal walls and the serous membranes lining the body cavities. These are the endothoracic, endoabdominal, and endopelvic ascias; the latter two may be reerred to collectively as extraperitoneal ascia. Unlike three-dimensional realized or actual spaces, these potential spaces have no depth; their walls are apposed with only a thin lm o lubricating fuid between them that is secreted by the enclosing membranes. When the wall is interrupted at any point, or when a fuid is secreted or ormed within them in excess, they become realized spaces; however, this condition is abnormal or pathological. Usually occurring in locations subject to riction, bursae enable one structure to move more reely over another. Subcutaneous bursae occur in the subcutaneous tissue between the skin and bony prominences, such as at the elbow or knee; subascial bursae lie beneath deep ascia; and subtendinous bursae acilitate the movement o tendons over bone. Synovial tendon sheaths are a specialized type o elongated bursae that wrap around tendons, usually enclosing them as they traverse osseobrous tunnels that anchor the tendons in place. Because they are ormed by delicate, transparent serous membranes and are collapsed, bursae are not easily noticed or dissected in the laboratory. It is possible to display bursae by injecting and distending them with colored fuid. This conguration is much like wrapping a large but empty balloon around a structure, such as a st. The object is surrounded by the two layers o the empty balloon but is not inside the balloon; the balloon itsel remains empty. For an even more exact comparison, the balloon should rst be lled with water and then emptied, leaving the empty balloon wet inside. Each lung is surrounded by-but is not inside-a pleural sac, and the abdominal viscera are surrounded by- but are not inside-the peritoneal sac. In such cases, the inner layer o the balloon or serous sac (the one adjacent to the st, viscus, or viscera) is called the visceral layer; the outer layer o the balloon (or the one in contact with the body wall) is called the parietal layer. Surgeons take advantage o these interascial planes, separating structures to create spaces that allow movement and access to deeply placed structures. In some procedures, surgeons use extrapleural or extraperitoneal ascial planes, which allow them to operate outside the membranes lining the body cavities, minimizing the potential or contamination, the spread o inection, and consequent ormation o adhesions (adherences) within the cavities. Unortunately, these planes are oten used and dicult to establish or appreciate in embalmed cadavers. The Bottom Line Integumentary system: the integumentary system (the skin) consists o the epidermis, dermis, and specialized structures (hair ollicles, sebaceous glands, and sweat glands). The skin: plays important roles in protection, containment, heat regulation, and sensation; synthesizes and stores vitamin D; eatures tension lines, relating to the predominant direction o collagen fbers in the skin, that have implications or surgery and wound healing. Fascias and bursae: Deep ascia is an organized connective tissue layer that completely envelops the body beneath the subcutaneous tissue underlying the skin. Extensions and modifcations o the deep ascia: divide muscles into groups (intermuscular septa), invest individual muscles and neurovascular bundles (investing ascia), lie between musculoskeletal walls and the serous membranes lining body cavities (subserous ascia), and hold tendons in place during joint movements (retinacula). Bursae are closed sacs ormed o serous membrane that occur in locations subject to riction; they enable one structure to move reely over another. Synovial tendon sheaths are longitudinal bursae that surround tendons as they pass deep to retinacula or through fbrous digital sheaths. Bursal sacs enclose several structures, such as the heart, lungs, abdominal viscera, and tendons, much like this collapsed balloon encloses the fst. A thin flm o lubricating uid between the parietal and visceral layers coners mobility to the structure surrounded by the bursa within a confned compartment. The transitional olds o synovial membrane between the continuous parietal and visceral layers surrounding the connecting stalks (the wrist in this example) and/or neurovascular structures serving the surrounded mass are called mesenteries. The appendicular skeleton consists o the bones o the limbs, including those orming the pectoral (shoulder) and pelvic girdles. Cartilage is a resilient, semirigid orm o connective tissue that orms parts o the skeleton where more fexibility is required-or example, where the costal cartilages attach the ribs to the sternum. Also, the articulating suraces (bearing suraces) o bones participating in a synovial joint are capped with articular cartilage that provides smooth, low-riction, gliding suraces or ree movement. The proportion o bone and cartilage in the skeleton changes as the body grows; the younger a person is, the more cartilage he or she has. Bone, a living tissue, is a highly specialized, hard orm o connective tissue that makes up most o the skeleton. Bones o the adult skeleton provide Support or the body and its vital cavities; it is the chie supporting tissue o the body. A continuous supply o new blood cells (produced by the marrow in the medullary cavity o many bones). A brous connective tissue covering surrounds each skeletal element like a sleeve, except where articular cartilage occurs; that surrounding bones is periosteum. The periosteum and perichondrium nourish the external aspects o the skeletal tissue. They are capable o laying down more cartilage or bone (particularly during racture healing) and provide the interace or attachment o tendons and ligaments. They are distinguished by the relative amount o solid matter and by the number and size o the spaces they contain. All bones have a supercial thin layer o compact bone around a central mass o spongy bone, except where the latter is replaced by a medullary (marrow) cavity. Articular facets of vertebra Of rib: Head Neck Tubercle Body Spinous process of vertebrae Within the medullary cavity o adult bones, and between the spicules (trabeculae) o spongy bone, yellow (atty) or red (blood cell and platelet orming) bone marrow-or a combination o both-is ound. The architecture and proportion o compact and spongy bone vary according to unction. In long bones designed or rigidity and attachment o muscles and ligaments, the amount o compact bone is greatest near the middle o the shat where the bones are liable to buckle. Right posterolateral view Humerus Capitulum Shaft Trochlea Greater trochanter of femur Ischial tuberosity Obturator foramen Classifcation o Bones Bones are classied according to their shape. Short bones are cuboidal and are ound only in the tarsus (ankle) and carpus (wrist). Other ormations relate to joints, the passage o tendons, and the provision o increased leverage. Facet: smooth fat area, usually covered with cartilage, where a bone articulates with another bone. The mesenchymal cells condense and dierentiate into chondroblasts, dividing cells in growing cartilage tissue, thereby orming a cartilaginous bone model. In the midregion o the model, the cartilage calcies (becomes impregnated with calcium salts), and periosteal capillaries (capillaries rom the brous sheath surrounding the model) grow into the calcied cartilage o the bone model and supply its interior. These blood vessels, together with associated osteogenic (bone-orming) cells, orm a periosteal bud. The capillaries initiate the primary ossifcation center, so named because the bone tissue it orms replaces most o the cartilage in the main body Epiphysial artery Periosteum Primary ossification center (diaphysis) Periosteal bud Cartilage 1 Secondary ossification center (epiphysis) Epiphysial plate Diaphysis Epiphysial plate Metaphysis Nutrient artery (derived from periosteal bud) Secondary ossification center (epiphysis) (A) Epiphysis Epiphysial plate Bone Development Most bones take many years to grow and mature. The humerus (arm bone), or example, begins to ossiy at the end o the embryonic period (8 weeks); however, ossication is not complete until age 20.

The type prostate 9 complex vitamin proscar 5 mg with amex, participating articular suraces prostate cancer foods order 5mg proscar mastercard, and ligaments o the joints o the thoracic wall are provided in Table 4 prostate medication order proscar amex. The intervertebral joints between the bodies o adjacent vertebrae are joined by longitudinal ligaments and A typical rib articulates posteriorly with the vertebral column at two joints prostate cancer questions for your doctor buy genuine proscar line, the joints o heads o ribs and costotransverse joints androgen hormone killing buy proscar once a day. The heads o the ribs connect so closely to the vertebral bodies that only slight gliding movements occur at the (demi)acets (pivoting around the intra-articular ligament o the head o the rib) prostate cancer outside the prostate best purchase for proscar. Abundant ligaments lateral to the posterior parts (vertebral arches) o the vertebrae provide strength to and limit the movements o these joints, which have only thin joint capsules. A costotransverse ligament passing rom the neck o the rib to the transverse process and a lateral costotransverse ligament passing rom the tubercle o the rib to the tip o the transverse process strengthen the anterior and posterior aspects o the joint, respectively. A superior costotransverse ligament is a broad band that joins the crest o the neck o the rib to the transverse process superior to it. The aperture between this ligament and the vertebra permits passage o the spinal nerve and the posterior branch o the intercostal artery. The strong costotransverse ligaments binding these joints limit their movements to slight gliding. However, the articular suraces on the tubercles o the superior 6 ribs are convex and it into concavities on the transverse processes. As a result, rotation occurs around a mostly transverse axis that traverses the intra-articular ligament and the head and neck o the rib. This results in elevation and depression movements o the sternal ends o the ribs and sternum in the sagittal plane (pump-handle movement). The weak joint capsules o these joints are thickened anteriorly and posteriorly to orm radiate sternocostal ligaments. These continue as thin, broad membranous bands passing rom the costal cartilages to the anterior and posterior suraces o the sternum, orming a elt-like covering or this bone. Movements o Thoracic Wall Movements o the thoracic wall and the diaphragm during inspiration produce increases in the intrathoracic volume and diameters o the thorax. Consequent pressure changes result in air being alternately drawn into the lungs (inspiration) through the nose, mouth, larynx, and trachea and expelled rom the lungs (expiration) through the same passages. During passive expiration, the diaphragm, intercostal muscles, and other muscles relax, decreasing intrathoracic volume and increasing the intrathoracic pressure. This allows the stretched elastic tissue o the lungs to recoil, expelling most o the air. The vertical dimension (height) o the central part o the thoracic cavity increases during inspiration as contraction o the diaphragm causes it to descend, compressing the abdominal viscera. During expiration, the vertical dimension returns to the neutral position as the elastic recoil o the lungs produces subatmospheric pressure in the pleural cavities, between the lungs and the thoracic wall. As a result o this and the absence o resistance to the previously compressed viscera, the domes o the diaphragm ascend, diminishing the vertical dimension. Because the ribs slope ineriorly, their elevation also results in anteroposterior movement o the sternum, especially its inerior end, with slight movement occurring at the manubriosternal joint in young people, in whom this joint has not yet synostosed (united). The transverse dimension o the thorax also increases slightly when the intercostal muscles contract, raising the middle (lateralmost parts) o the ribs (especially the lower ones)-the bucket-handle movement. The combination o all these movements moves the thoracic cage anteriorly, superiorly, and laterally. The middle parts o the lower ribs move laterally when they are elevated, increasing the transverse dimension (bucket-handle movement). The primary movement o inspiration (resting or orced) is contraction o the diaphragm, which increases the vertical dimension o the thoracic cavity (arrows). When the diaphragm relaxes, decompression o the abdominal viscera pushes the diaphragm upward, reducing the vertical dimension or expiration. However, chest pain may also occur in intestinal, gallbladder, and musculoskeletal disorders. When evaluating a patient with chest pain, the examination is largely concerned with discriminating between serious conditions and the many minor causes o pain. People who have had a heart attack usually describe the associated pain as a "crushing" substernal pain (deep to the sternum) that does not disappear with rest. Fractures o the lower ribs may tear the diaphragm and result in a diaphragmatic hernia (see Chapter 5, Abdomen). Rib ractures are painul because the broken parts move during respiration, coughing, laughing, and sneezing. Rib ractures have been surgically plated or repaired or this reason, but the practice remains controversial. Flail Chest Multiple rib ractures may allow a sizable segment o the anterior and/or lateral thoracic wall to move reely. The loose segment o the wall moves paradoxically (inward on inspiration and outward on expiration). Flail chest is an extremely painul injury and impairs ventilation, thereby aecting oxygenation o the blood. During treatment, the loose segment may be internally xed with plates or wires to prevent movement. Rib Fractures the short, broad 1st rib, postero-inerior to the clavicle, is rarely ractured because o its protected position (it cannot be palpated). Consequently, a rst rib racture is commonly viewed as a hallmark o severe injury in blunt trauma. When it is broken, however, structures crossing its superior aspect may be injured, including the brachial plexus o nerves and subclavian vessels that serve the upper limb. Rib spreader Parietal pleura (cut) Thoracic Wall 303 o costal cartilage to gain entrance to the thoracic cavity. In general, a lateral approach is most satisactory or entry through the thoracic cage. This elevates and laterally rotates the inerior angle o scapula, allowing access as high as the 4th intercostal space. Most commonly, rib retraction allows procedures to be perormed through a single intercostal space ollowing rib retraction, with care to avoid the superior neurovascular bundle. I wider exposure is required, surgeons use an H-shaped incision to incise the supercial aspect o the periosteum that ensheathes the rib, strip the periosteum rom the rib, and then excise a wide segment o the rib to gain better access, as might be required to enter the thoracic cavity and remove a lung (pneumonectomy), or example. Ater the operation, the missing pieces o ribs regenerate rom the intact periosteum, although imperectly. In many cases, intrathoracic surgery can be perormed using a minimally invasive endoscopic approach (see the Clinical Box "Thoracoscopy" in this chapter). Ossifed Xiphoid Process People in their early 40s may suddenly become aware o their partly ossied xiphoid process and consult their physician about the hard lump in the "pit o their stomach" (epigastric ossa). Never having been aware o their xiphoid process beore, they ear they have developed a tumor. Such injuries o the cartilage can result in heterotropic ossication o the upper part o the incision. Sternal Fractures Despite the subcutaneous location o the sternum, sternal ractures are not common. The installation and use o air bags in vehicles has reduced the number o sternal ractures. A racture o the sternal body is usually a comminuted racture (a break resulting in several pieces). Displacement o the bone ragments is uncommon because the sternum is invested by deep ascia (brous continuities o radiate sternocostal ligaments;. The most common site o sternal racture in elderly people is at the sternal angle, where the manubriosternal joint has used. The concern in sternal injuries is not primarily or the racture itsel, but or the likelihood o heart injury (myocardial contusion, cardiac rupture, tamponade) and/or lung injury. Patients with sternal contusion should be evaluated or underlying visceral injury (Marx et al. Resection may be required to relieve pressure on these structures, which can be perormed through a transaxillary approach (incision in axillary ossa or armpit). Supernumerary (extra) ribs also have clinical signicance in that they may conuse the identication o vertebral levels in radiographs and other diagnostic images. Median Sternotomy To gain access to the thoracic cavity or surgical operations in the mediastinum, the sternum is divided (split) in the median plane and retracted, or example, or coronary artery bypass grating. The fexibility o ribs and costal cartilages enables spreading o the halves o the sternum during procedures requiring median sternotomy. Such "sternal splitting" also gives good exposure or removal o tumors in the superior lobes o the lungs. Recovery is less painul than when a muscle-splitting thoracotomy incision is used (see previous Clinical Box, "Thoracotomy, Intercostal Space Incisions, and Rib Excision"). Protective Function and Aging o Costal Cartilages Costal cartilages provide resilience to the thoracic cage, preventing many blows rom racturing the sternum and/or ribs. In elderly people, the costal cartilages lose some o their elasticity and become brittle; they may undergo calcication, making them radiopaque. Consequently, 304 Chapter 4 Thorax Sternal Biopsy the sternal body is oten used or bone marrow needle biopsy because o its breadth and subcutaneous position. The needle rst pierces the thin cortical bone and then enters the vascular spongy bone. Sternal biopsy is commonly used to obtain specimens o marrow or transplantation and or detection o metastatic cancer and blood dyscrasias (abnormalities). Rib dislocations are common in body contact sports; complications may result rom pressure on or damage to nearby nerves, vessels, and muscles. Displacement o interchondral joints usually occurs unilaterally and involves ribs 8, 9, and 10. Trauma sucient to displace these joints oten injures underlying structures, such as the diaphragm and/or liver, causing severe pain, particularly during deep inspiratory movements. Sternal Anomalies the sternum develops through the usion o bilateral, vertical condensations o precartilaginous tissue, sternal bands or bars. Complete sternal clet is an uncommon anomaly through which the heart may protrude (ectopia cordis). Partial clets involving the manubrium and superior hal o the body are V- or U-shaped and can be repaired during inancy by direct apposition and ixation o the sternal halves. Sometimes a peroration (sternal oramen) remains in the sternal body because o incomplete usion. It is not clinically signiicant; however, one should be aware o its possible presence so that it will not be misinterpreted in chest X-ray, or example, as an unhealed bullet wound. The xiphoid process is commonly perorated in elderly persons because o age-related changes; this peroration is also not clinically signicant. Similarly, an anteriorly protruding xiphoid process in neonates is not unusual; when it occurs, it does not usually require correction. Separation o Ribs "Rib separation" reers to dislocation o the costochondral junction between the rib and its costal cartilage. Paralysis o Diaphragm Paralysis o hal o the diaphragm (one dome or hemidiaphragm) because o injury to its motor supply rom the phrenic nerve does not aect the other hal since the domes are separately supplied by the right and let phrenic nerves. One can detect paralysis o the diaphragm radiographically by noting its paradoxical movement. Instead o descending as it normally does during inspiration owing to diaphragmatic contraction. Instead o ascending during expiration, the paralyzed dome descends in response to the positive pressure in the lungs. Inspiration Resting (normal expiration) Thoracic Outlet Syndrome Anatomists reer to the superior thoracic aperture as the thoracic inlet because noncirculating substances (air and ood) may enter the thorax only through this aperture. When clinicians reer to the superior thoracic aperture as the thoracic outlet, they are emphasizing the arteries and T1 spinal nerves that emerge rom the thorax through this aperture to enter the lower neck and upper limbs. The domed shape o the thoracic cage gives it strength, and its osteocartilaginous elements and joints give it exibility. Laterally and anteriorly, the cage consists o 12 ribs that are continued anteriorly by costal cartilages. Apertures o thoracic wall: Although the thoracic cage is complete peripherally, it is open superiorly and ineriorly. The superior thoracic aperture is a small passageway or the transmittal o structures to and rom the neck and upper limbs. The large inerior thoracic aperture provides a rim to which the diaphragm is attached. Joints o thoracic wall: the joints enable and determine movements o the thoracic wall. Posteriorly, ribs articulate with the semiexible thoracic vertebral column via costovertebral joints. These include joints o heads o ribs and costotransverse joints, both strongly supported by multiple ligaments.

However prostate medication over the counter order proscar in united states online, movement o the kidneys occurs during respiration and when changing rom the supine to the erect position prostate cancer hereditary purchase proscar line, and vice versa prostate keyhole surgery purchase proscar no prescription. Normal renal mobility is approximately 3 cm man health advice proscar 5mg low cost, approximately the height o one vertebral body mens health old school workout purchase cheap proscar line. Superiorly prostate cancer kidney metastasis purchase proscar paypal, the renal ascia is continuous with the ascia on the inerior surace o the diaphragm (diaphragmatic ascia); thus, the primary attachment o the suprarenal glands is to the diaphragm. Ineriorly, the anterior and posterior layers o renal ascia are only loosely united, i attached at all. Abdominal Viscera 517 At the concave medial margin o each kidney is a vertical clet, the renal hilum. Structures that serve the kidneys (vessels, nerves, and structures that drain urine rom the kidney) enter and exit the renal sinus through the renal hilum. The hilum o the let kidney lies near the transpyloric plane, approximately 5 cm rom the median plane. The transpyloric plane passes through the superior pole o the right kidney, which is approximately 5. During lie, the kidneys are reddish brown and measure approximately 10 cm in length, 5 cm in width, and 5. Superiorly, the posterior aspects o the kidneys are associated with the diaphragm, which separates them rom the pleural cavities and the 12th pair o ribs. More ineriorly, the posterior suraces o the kidney are related to the psoas major muscles medially and the quadratus lumborum muscle. The subcostal nerve and vessels and the iliohypogastric and ilio-inguinal nerves Median plane Scapular line Diaphragm Liver Spleen T10 T11 Transpyloric plane Left kidney 12th rib Right kidney Ureter Iliac crest Ilium Dimple indicating posterior superior iliac spine T12 L1 5cm descend diagonally across the posterior suraces o the kidneys. The let kidney is related to the stomach, spleen, pancreas, jejunum, and descending colon. At the hilum, the renal vein is anterior to the renal artery, which is anterior to the renal pelvis. Within the kidney, the renal sinus is occupied by the renal pelvis, calices, vessels, and nerves and a variable amount o at. Each kidney has anterior and posterior suraces, medial and lateral margins, and superior and inerior poles. However, because o the protrusion o the lumbar vertebral column into the abdominal cavity, the kidneys are obliquely placed, lying at an angle to each other. Consequently, the transverse diameter o the kidneys is oreshortened in anterior views. The lateral margin o each kidney is convex, and the medial margin is concave where the renal sinus and renal pelvis are located. The renal pelvis is the fattened, unnel-shaped expansion o the superior end o the ureter. The renal pelvis receives two or three major calices (calyces), each o which divides into two or three minor calices. Each minor calyx is indented by a renal papilla, the apex o the renal pyramid, rom which the urine is excreted. The lobes are visible on the external suraces o the kidneys in etuses, and evidence o the lobes may persist or some time ater birth. They run ineriorly rom the apices o the renal pelves at the hila o the kidneys, passing over the pelvic brim at the biurcation o the common iliac arteries. The abdominal parts o the ureters adhere closely to the parietal peritoneum and are retroperitoneal throughout their course. From the back, the surace marking o the ureter is a line joining a point 5 cm lateral to the L1 spinous process and the posterior superior iliac spine. The ureters occupy a sagittal plane that intersects the tips o the transverse processes o the lumbar vertebrae. The anterior lip o the renal hilum has been cut away to expose the renal pelvis and calices within the renal sinus. The renal pyramids contain the collecting tubules and orm the medulla o the kidney. These constricted areas are potential sites o obstruction by ureteric stones (calculi). The suprarenal glands are enclosed by renal ascia by which they are attached to the crura o the diaphragm. Although the name "suprarenal" implies that the kidneys are their primary relationship, their major attachment is to the diaphragmatic crura. They are separated rom the kidneys by a thin septum (part o the renal ascia-see the Clinical Box "Renal Transplantation," p. The crescent-shaped let gland is medial to the superior hal o the let kidney and is related to the spleen, stomach, pancreas, and the let crus o the diaphragm. Each gland has a hilum, where the veins and lymphatic vessels exit the gland, whereas the arteries and nerves enter the glands at multiple sites. Each suprarenal gland has two parts: the suprarenal cortex and suprarenal medulla. The suprarenal cortex derives rom mesoderm and secretes corticosteroids and androgens. These hormones cause the kidneys to retain sodium and water in response to stress, increasing the blood volume and blood pressure. The suprarenal medulla is a mass o nervous tissue permeated with capillaries and sinusoids that derives rom neural crest cells associated with the sympathetic nervous system. The chroman cells o the medulla are related to sympathetic ganglion (postsynaptic) neurons in both derivation (neural crest cells) and unction. These cells secrete catecholamines (mostly epinephrine) into the bloodstream in response to signals rom presynaptic neurons. Powerul medullary hormones, epinephrine (adrenaline) and norepinephrine (noradrenaline), activate the body to a fight-or-ght status in response to traumatic stress. They also increase heart rate and blood pressure, dilate the bronchioles, and change blood fow patterns, preparing or physical exertion. Contrast medium was injected into the ureters rom a exible endoscope (urethroscope) in the bladder. Sites at which relative constrictions in the ureters normally appear: (1) at the ureteropelvic junction, (2) crossing the external iliac artery and/or pelvic brim, and (3) as the ureter traverses the bladder wall. The celiac plexus o nerves and ganglia that surrounds the celiac trunk has been removed. The inerior vena cava has been transected, and its superior part has been elevated rom its normal position to reveal the arteries that pass posterior to it. A cross section o the suprarenal gland (inset) shows that it is composed o two distinct parts: the cortex and medulla, which are two separate endocrine glands that became closely related during embryonic development. The posterior segmental artery, which originates rom a continuation o the posterior branch o the renal artery, supplies the posterior segment o the kidney. Extrahilar renal arteries rom the renal artery or aorta may enter the external surace o the kidney, commonly at their poles ("polar arteries"-see the Clinical Box "Accessory Renal Vessels," p. Several renal veins drain each kidney and unite in a variable ashion to orm the right and let renal veins; these veins lie anterior to the right and let renal arteries. Arterial branches to the abdominal portion o the ureter arise consistently rom the renal arteries, with less constant branches arising rom the testicular or ovarian arteries, the abdominal aorta, and the common iliac arteries. Although the veins o the kidney anastomose reely, segmental arteries are end arteries. However, ureteric branches are small and relatively delicate, and disruption may lead to ischemia in spite o the continuous anastomotic channel ormed. In operations in the posterior abdominal region, surgeons pay special attention to the location o ureters and are careul not to retract them laterally or unnecessarily. The arteries supplying the pelvic portion o the ureter are discussed in Chapter 6, Pelvis and Perineum. Veins draining the abdominal part o the ureters drain into the renal and gonadal (testicular or ovarian) veins. The endocrine unction o the suprarenal glands makes their abundant blood supply necessary. The renal lymphatic vessels ollow the renal veins and drain into the right and let lumbar (caval and aortic) lymph nodes. Lymphatic vessels rom the superior part o the ureter may join those rom the kidney or pass directly to the lumbar nodes. Lymphatic vessels rom the middle part o the ureter usually drain into the common iliac lymph nodes, whereas vessels rom its inerior part drain into the common, external, or internal iliac lymph nodes. The suprarenal lymphatic vessels arise rom a plexus deep to the capsule o the gland and rom one in its medulla. The nerves to the kidneys arise rom the renal nerve plexus and consist o sympathetic and parasympathetic bers. The renal nerve plexus is supplied by bers rom the abdominopelvic (especially the least) splanchnic nerves. The lymphatic vessels o the kidneys orm three plexuses: one in the substance o the kidney, one under the fbrous capsule, and one in the perirenal at. Four or fve lymphatic trunks leave the renal hilum and are joined by vessels rom the capsule (arrows). The lymphatic vessels ollow the renal vein to the lumbar (caval and aortic) lymph nodes. The nerves o the kidneys and suprarenal glands are derived rom the celiac plexus, abdominopelvic (lesser and least) splanchnic nerves, and the aorticorenal ganglion. The main eerent innervation o the kidney is vasomotor, autonomic nerves supplying the aerent and eerent arterioles. Exclusively in the case o the suprarenal medulla, the presynaptic sympathetic fbers pass through both the paravertebral and prevertebral ganglia without synapsing to end directly on the secretory cells o the suprarenal medulla. Ureteric pain is usually reerred to the ipsilateral lower quadrant o the anterior abdominal wall and especially to the groin (see the Clinical Box "Renal and Ureteric Calculi," p. The rich nerve supply o the suprarenal glands is rom the celiac plexus and abdominopelvic (greater, lesser, and least) splanchnic nerves. In lean adults, the inerior pole o the right kidney is palpable by bimanual examination as a rm, smooth, somewhat rounded mass that descends during inspiration. To palpate the kidneys, press the fank (side o the trunk between the 11th and 12th ribs and the iliac crest) anteriorly with one hand while palpating deeply at the costal margin with the other. The let kidney is usually not palpable unless it is enlarged or a retroperitoneal mass has displaced it ineriorly. Nephroptosis Because the layers o renal ascia do not use rmly ineriorly to oer resistance, abnormally mobile kidneys may descend more than the normal 3 cm when the body is erect. When kidneys descend, the suprarenal glands remain in place because they lie in a separate ascial compartment and are rmly attached to the diaphragm. Nephroptosis (dropped kidney) is distinguished rom an ectopic kidney (congenital misplaced kidney) by a ureter o normal length that has loose coiling or kinks because the distance to the bladder has been reduced. Symptoms o intermittent pain in the renal region, relieved by lying down, appear to result rom traction on the renal vessels. The lack o inerior support or the kidneys in the lumbar region is one o the reasons transplanted kidneys are placed in the iliac ossa o the greater pelvis. Other reasons or this placement are the availability o major blood vessels and convenient access to the nearby bladder. For example, ascia at the renal hilum attaches to the renal vessels and ureter, usually preventing the spread o pus to the contralateral side. However, pus rom an abscess (or blood rom an injured kidney) may Renal Transplantation Renal transplantation is the preerred treatment or selected cases o chronic renal ailure. The kidney can be removed rom the donor without damaging the suprarenal gland because o the weak septum o renal ascia that separates the kidney rom this gland. This site supports the transplanted kidney, so that traction is not placed on the surgically anastomosed vessels. The patient previously had a right nephrectomy because o complications that developed in the right kidney, and his advanced renal ailure has been treated with renal transplantation. Pain in Pararenal Region the close relationship o the kidneys to the psoas major muscles explains why extension o the hip joints may increase pain resulting rom infammation in the pararenal areas. The syndrome may include hematuria or proteinuria (blood or protein in the urine), abdominal (let fank) pain, nausea and vomiting (indicating compression o the duodenum), and let testicular pain in men (related to the let testicular vein draining into the let renal vein proximal to the compression). Congenital Anomalies o Kidneys and Ureters Bid renal pelvis and ureter are airly common. These anomalies result rom division o the ureteric bud (metanephric diverticulum), the primordium o the renal pelvis and ureter. The extent o ureteral duplication depends on the completeness o embryonic division o the ureteric bud. The bid renal pelvis and/or ureter may be unilateral or bilateral; however, separate openings into the bladder are uncommon. Incomplete division o the ureteric bud results in a bid ureter; complete division results in a supernumerary kidney (Moore, Persaud, and Torchia, 2016). In approximately 1 in 600 etuses, the inerior poles (rarely, the superior poles) o the kidneys use to orm a horseshoe kidney. This U-shaped kidney usually lies at Accessory Renal Vessels During their "ascent" to their nal site, the embryonic kidneys receive their blood supply and venous drainage rom successively more superior vessels. Variations in the number and position o these vessels occur in approximately 30% o people.

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