Digestive System Anatomy PDF

Describe the structures providing passage for food from the mouth to the rectum. The structures providing passage for food from the mouth to the rectum are: ● Mouth ● Pharynx ● Esophagus ● Stomach ● Small intestine (duodenum, jejunum, ileum) ● Large intestine (cecum, colon, rectum, anal canal) At wh...

Describe the structures providing passage for food from the mouth to the rectum. The structures providing passage for food from the mouth to the rectum are: ● Mouth ● Pharynx ● Esophagus ● Stomach ● Small intestine (duodenum, jejunum, ileum) ● Large intestine (cecum, colon, rectum, anal canal) At what vertebral level does the esophagus pass through the diaphragm? Enter the stomach? ● The esophagus passes through the diaphragm at the level of T10 vertebra. ● It enters the stomach at the esophagogastric junction at the level of T11 vertebra. Describe the morphology, arterial supply, venous drainage and lymphatic drainage of the esophagus. ● The esophagus has an outer longitudinal and inner circular layer of smooth muscle in its lower third and both circular and longitudinal layers of skeletal muscle in its upper third. ● Arterial supply is from esophageal branches of left gastric artery and left inferior phrenic artery. ● Venous drainage is primarily to portal system via left gastric vein. ● Lymphatic drainage is to esophageal lymph nodes near bifurcation of trachea. Describe the morphology, arterial supply, venous drainage and lymphatic drainage of the stomach. ● Morphology: Fundus, body, pyloric antrum, pyloric canal. Lesser and greater curvatures. ● Arterial supply: Left and right gastric, right and left gastro-omental, short and posterior gastric arteries (from celiac trunk). ● Venous drainage: Right and left gastric veins --> Portal vein ● Lymphatic drainage: Along curvatures to pyloric nodes --> Celiac nodes Describe/ Draw the branches of the celiac trunk, superior mesenteric artery, inferior mesenteric artery. Celiac Trunk: ● Left gastric artery ● Splenic artery ● Common hepatic artery --> Proper hepatic artery, gastroduodenal artery Superior mesenteric artery: ● Inferior pancreaticoduodenal artery ● Jejunal and ileal arteries ● Ileocolic, right colic, middle colic arteries Inferior mesenteric artery: ● Left colic artery ● Sigmoid arteries ● Superior rectal artery Describe/ Draw the venous drainage of the gut structures. ● Esophagus: Left gastric vein --> Portal vein ● ● ● ● Stomach: Right and left gastric veins --> Portal vein Small intestine: Superior mesenteric vein --> Portal vein Large intestine: Inferior mesenteric vein --> Splenic vein --> Portal vein Rectum: Superior rectal vein --> Inferior mesenteric vein --> Portal vein Where do the portal and systemic venous systems anastomose? ● At capillary beds of the liver sinusoidal system. ● Esophageal veins connecting to azygos vein. ● Veins accompanying superior and inferior pancreaticoduodenal arteries. ● Hemorrhoidal veins. What surface landmarks could I use for each part of the stomach (practice this on the skeletons in lab!) ● Fundus: Under left dome of diaphragm, around level of 5th intercostal space ● Cardia: Left of midline at level of 7th left costal cartilage ● Body: Between fundus and pyloric antrum, central epigastric region ● Pyloric antrum: Right upper quadrant At what vertebral level does each part of the duodenum lie? What are the other relations of the duodenum? Is it intraperitoneal, retroperitoneal or both? ● Duodenum is mostly retroperitoneal, except for initial part which is intraperitoneal. ● First part (superior): L1 vertebra level ● Second part (descending): L2-L3 vertebrae ● Third part (horizontal): L3 vertebra ● Fourth part (ascending): L3 vertebra Other relations: ● Sweeps across bodies of L1-L3 vertebrae ● Crosses IVC, aorta, superior mesenteric vessels ● Head of pancreas is within concavity of duodenum The duodenum is derived partly from the foregut and partly from the midgut. This should help you be able to describe the complex vasculature and lymphatics of the duodenum. ● Proximal duodenum supplied by branches of gastroduodenal artery (celiac trunk) ● Distal duodenum supplied by superior and inferior pancreaticoduodenal arteries (SMA) ● Forms an important arterial anastomosis between celiac and SMA systems ● Proximal duodenal drainage to pyloric nodes --> celiac nodes ● Distal duodenal drainage to pancreaticoduodenal nodes --> superior mesenteric nodes How can you distinguish the jejunum and ileum in terms of their structure and vasculature? ● Jejunum: More wide diameter, thicker walls, more vascular. Jejunal arteries have arcade pattern. ● Ileum: Narrower diameter, thinner walls, less vascular. Ileal arteries directly penetrate mesentery. Be able to describe the vasculature, lymphatics and innervation of the large and small intestines, liver, gall bladder, pancreas, spleen (and stomach and esophagus but this was from the last reading) Small intestine: Arterial supply: SMA and branches Venous drainage: SMV --> Portal vein Lymphatics: Mesenteric nodes --> Celiac nodes Innervation: Vagus nerves (parasympathetic), Greater/Lesser splanchnic nerves (sympathetic) Large intestine: ● Arterial supply: IMA and branches ● Venous drainage: IMV --> Splenic vein --> Portal vein ● Lymphatics: Paracolic, intermediate mesenteric nodes --> Inferior mesenteric nodes ● Innervation: Vagus nerves (parasympathetic), Lumbar splanchnic nerves (sympathetic) Liver: ● Arterial supply: Hepatic artery (proper/common) ● Venous drainage: Hepatic veins --> IVC ● Lymphatics: Hepatic nodes along portal triads --> Celiac nodes ● Innervation: Hepatic plexus (vagus nerves, sympathetics from celiac plexus) Gallbladder: ● Arterial supply: Cystic artery from right hepatic artery ● Venous drainage: Cystic vein --> Portal vein ● Lymphatics: Cystic node --> Hepatic nodes ● Innervation: Hepatic plexus Pancreas: ● Arterial supply: Pancreatic branches of splenic artery, superior/inferior pancreaticoduodenal arteries ● Venous drainage: Pancreatic veins --> Splenic vein --> Portal vein ● Lymphatics: Pancreaticosplenic nodes --> Celiac nodes ● Innervation: Pancreatic plexus Spleen: ● Arterial supply: Splenic artery ● Venous drainage: Splenic vein --> Portal vein ● Lymphatics: Hilum --> Celiac nodes ● Innervation: Splenic plexus What are the tenaie coli, haustra and epiploic (omental) appendices of the large intestines? ● Teniae coli: Three longitudinal bands of smooth muscle on exterior surface ● Haustra: Sacculations on exterior surface between teniae ● Epiploic appendages: Small fat accumulations under serosa attached to colon Describe the parts of the pancreas and their major relations. ● Head: In concavity of duodenum ● Neck: Anterior to origin of SMA ● Body: Anterior to L1-2 vertebrae ● Tail: Reaches hilum of spleen Describe the morphology of the biliary ducts and the hepatopancreatic ampulla region ● Right and left hepatic ducts --> Common hepatic duct ● ● ● ● Cystic duct from gallbladder joins common hepatic duct --> Common bile duct Common bile duct joins with main pancreatic duct at hepatopancreatic ampulla --> enters duodenum Describe the parts of the liver and their major relations. ● Right lobe: Larger, separated by falciform ligament ● Left lobe: Smaller, contacts stomach ● Quadrate lobe: Inferior, contacts gallbladder ● Caudate lobe: Posterior, near IVC ● Porta hepatis: Where vessels/ducts enter/exit Relations: ● Superior - Diaphragm ● Inferior - Stomach, duodenum, right colic flexure ● Posterior - IVC, crura of diaphragm ● Anterior - Xiphoid process, costal margin What are the surface relations of the spleen, pancreas and liver? Spleen: ● Superior - Diaphragm ● Inferior - Splenic flexure of colon ● Medial - Stomach, left kidney ● Lateral - 9th-11th ribs Pancreas: ● Anterior - Stomach, transverse colon, small intestine ● Posterior - IVC, aorta, left kidney ● Superior - Splenic vein, splenic artery ● Inferior - Duodenum, jejunum Liver: ● Superior - Diaphragm ● Inferior - Stomach, duodenum, right colic flexure ● Posterior - IVC, crura of diaphragm ● Anterior - Xiphoid process, costal margin Jump ahead to figure 5.54 and 5.57 and the clinical box (with Figure B5.13) as you learn the autonomic and sensory innervation of gut structures. In this figure and the clinical box below it you can learn the segmental sympathetic innervation of the gut structure which will help you infer (although some are not entirely obvious) the regions of referred pain for each gut structure. ● Esophagus: T5-9 sympathetic, vagus parasympathetic ● Stomach: T6-9 sympathetic, vagus parasympathetic ● Small intestine: T7-11 sympathetic, vagus parasympathetic ● Large intestine: T10-L2 sympathetic, vagus parasympathetic ● Rectum: S2-4 sympathetic, pelvic splanchnic parasympathetic Referred pain: ● Esophagus: Mid-chest or between shoulder blades ● Stomach: Epigastric region ● ● ● Small intestine: Periumbilical region ● Large intestine: Lower abdomen ● Rectum: Sacral region Describe the layers of fat and fascia around the kidneys ● Anterior pararenal fat between peritoneum and anterior renal fascia ● Perirenal fat capsule surrounds kidneys and adrenal glands ● Posterior pararenal fat between posterior renal fascia and transversalis fascia What are the relationships of the right and left kidneys? ● Right kidney lower than left (due to liver) ● Left kidney contacts spleen, pancreas, stomach ● Right kidney contacts liver, duodenum, colon Describe the vasculature of a) the kidneys and b) the ureters Kidneys: ● Arterial supply: Renal arteries - segmental, lobar, interlobar, arcuate, interlobular arteries ● Venous drainage: Renal vein on each side draining directly into IVC Ureters: ● Arterial supply: Renal, gonadal, aortic, common iliac, uterine, vaginal arteries ● Venous drainage: Gonadal, common iliac, uterine, vaginal veins What are the relationships of the structures at the hilus (hilum) of the kidney? ● Renal vein anterior ● Renal artery posterior ● Pelvis of ureter inferior ● Lymphatics and nerves Name the 3 main normal constrictions of the ureters 1. Ureteropelvic Junction: The first main constriction of the ureters is at the junction between the ureters and the renal pelves. This is where the urine from the kidneys enters the ureters. The constriction at this junction helps prevent the backflow of urine from the ureters into the kidneys. 2. Crossing External Iliac Vessels and/or Pelvic Brim: The second main constriction occurs as the ureters cross the external iliac vessels and/or the pelvic brim. This constriction helps prevent the backflow of urine from the bladder into the ureters. 3. Ureter Traversing Bladder Wall: The third main constriction is during the passage of the ureters through the wall of the urinary bladder. This constriction helps prevent the backflow of urine from the bladder into the ureters. Be able to identify the following structures: renal cortex, renal medulla, renal pyramid, renal column, major and minor calyces, papilla, renal pelvis, adrenal (suprarenal) cortex, adrenal (suprarenal) medulla ● Cortex: Outer region, separated into renal columns ● Medulla: Inner region, divided into renal pyramids ● Minor calyces: Cup-like strucures that surround papillae at apex of pyramids ● Major calyces: Formed by union of two or more minor calyces ● Renal pelvis: Funnel shaped dilation that narrows to become ureter ● Adrenal cortex: Outer yellowish lipid rich layer ● Adrenal medulla: Inner reddish chromaffin layer Describe the blood supply and drainage of the adrenal (suprarenal) glands? ● Arterial supply: Superior, middle, inferior suprarenal arteries from aorta ● Venous drainage: Right - short vein to IVC, Left - long vein to left renal vein How do the left and right adrenal (suprarenal) glands differ from one another ● Right adrenal gland: Pyramidal, intimate association with liver ● Left adrenal gland: Crescentic, more intimate association with kidney Be able to describe the sympathetic (including what LEVEL lateral horns!) and parasympathetic innervation to the structures of the gut. Be able to describe the pathway of general sensation of the major structures in the gut and, importantly, WHERE pain refers (especially structures such as appendix, gall bladder, stomach, kidneys/ureters, duodenum/pancreas head) Sympathetic innervation: ● Esophagus: T5-9 lateral horn ● Stomach: T6-9 lateral horn ● Small intestine: T7-11 lateral horn ● Large intestine: T10-L2 lateral horn ● Rectum: S2-4 lateral horn Parasympathetic innervation: ● Esophagus to transverse colon - vagus nerves ● Rectum - pelvic splanchnic nerves ● Referred pain: ● Esophagus: Mid chest or between shoulder blades ● ● ● ● ● ● ● ● Stomach: Epigastric region Small intestine: Periumbilical Large intestine: Lower abdominal quadrants Appendix: Right lower quadrant (McBurney's point) Rectum: Sacral region Kidney: Flank or back Ureter: Flank, groin, labia, scrotum Duodenum: Epigastric region Describe the diaphragm - what level? What is it's shape? Where do the crura attach? ● Musculofibrous partition between thorax and abdomen ● Dome shaped - superior concave, inferior convex ● Crura attach to lumbar vertebrae ● Level of T12-L3 vertebrae What are the main openings in the diaphragm and what goes through them? ● Caval opening: IVC ● Esophageal hiatus: Esophagus, anterior and posterior vagal trunks ● Aortic hiatus: Aorta, thoracic duct ● Foramina for greater, lesser, least splanchnic nerves Describe the vasculature and innervation of the diaphragm. Where does pain refer? ● Arterial supply: Musculophrenic, pericardiacophrenic arteries ● Venous drainage: Musculophrenic, pericardiacophrenic veins ● Innervation: Phrenic nerves (C3-5) ● Referred pain: Shoulder tip Learn the nerves of the lumbar plexus - ventral rami from which they are derived and what they innervate Lumbar plexus nerves and origin: ● Iliohypogastric: L1 ● Ilioinguinal: L1 ● Genitofemoral: L1-2 ● Lateral femoral cutaneous: L2-3 ● Femoral: L2-4 ● Obturator: L2-4 ● Lumbosacral trunk: L4-5 Structures innervated: ● Iliopsoas, quadriceps (femoral n.) ● Thigh muscles, hip/knee joints (obturator n.) ● Cremaster, labia/scrotum (genitofemoral n.) ● Lateral thigh skin (lateral femoral cutaneous n.) ● Lower abdominal wall (iliohypogastric, ilioinguinal nn.) Learn the attachments and actions of the psoas major, quadratus lumborum, iliacus Psoas major: ● Origin: Transverse processes of L1-5 vertebrae ● Insertion: Lesser trochanter of femur ● Action: Flexes hip, laterally flexes spine Quadratus lumborum: ● Origin: Iliolumbar ligament, iliac crest ● Insertion: 12th rib, lumbar transverse processes ● Action: Extends and laterally flexes vertebral column Iliacus: ● Origin: Iliac fossa, ala of sacrum ● Insertion: Lesser trochanter of femur ● Action: Flexion of hip joint Learn the branches of the aorta and IVC supplying the posterior abdominal wall. From abdominal aorta: ● Inferior phrenic arteries ● Lumbar arteries ● Middle sacral artery Tributaries of IVC: ● Lumbar veins ● Right/left ascending lumbar veins What are the intestinal and lumbar (paravertebral) trunks? What structures drain to each? ● Intestinal lymphatic trunks: Drain small intestine, large intestine, pancreas, spleen to cisterna chyli ● Lumbar (paravertebral) trunks: Drain kidneys, ureters, abdominal wall to cisterna chyli The intestinal and lumbar lymphatic trunks drain into the cisterna chyli. What separates the perineum from the pelvis? The perineum is separated between the thighs and buttocks What are the boundaries of the anal triangle and the urogenital triangle? ● Laterally by the ischium and the inferior part of the obturator internus, covered with obturator fascia ● Medially by the external anal sphincter, with a sloping superior medial wall or roof formed by the levator ani as it descends to blend with the sphincter; both structures surround the anal canal. ● Posteriorly by the sacrotuberous ligament and gluteus maximus ● Anteriorly by the bodies of the pubic bones, inferior to the origin of the puborectalis; these parts of the fossae, extending into the UG triangle superior to the perineal membrane, are known as the anterior recesses of the ischio-anal fossae. Where is the perineal body? Anococcygeal raphe? The perineal body is situated between the anal canal and the perineal membrane, beneath the skin and behind the genital vestibule or bulb of the penis. It connects with the back edge of the perineal membrane and upwards with the rectovesical or rectovaginal septum. The anococcygeal raphe (see image below) is a fibrous band that extends from the coccyx to the anus. It is not the same as the perineal body, but it is located in the same region. The fatty layer of subcutaneous tissue in the labia major and mons pubis is continuous with the _____CAMPERS______ fascia in the abdomen. The _______________MEMBRANOUS_____ layer of superficial fascia in the perineum is continuous with the membranous superficial fascia in other regions (Scarpa's fascia, Dartos fascia). The ___________PERINEAL_____ fascia invests the ischiocavernosus, bulbospongiosus, and superficial transverse perineal muscles and is continuous with the deep fascia over the external abdominal oblique muscles. What structures can be found in the superficial perineal pouch in: In males, the superficial perineal pouch contains the following structures: ● Root (bulb and crura) of the penis and associated muscles (ischiocavernosus and bulbospongiosus) ● Proximal (bulbous) part of the spongy urethra ● Superficial transverse perineal muscles ● Deep perineal branches of the internal pudendal vessels and pudendal nerves In females, the superficial perineal pouch contains the following structures: ● Clitoris and associated muscle (ischiocavernosus) ● Bulbs of the vestibule and the surrounding muscle (bulbospongiosus) ● Greater vestibular glands The external urethral sphincter is in the __deep perineal pouch. Describe the path of urine that would result from a tear in the spongy urethra. Between what layers does it travel in the abdomen? perineum? Penis? ● When there's a tear in the spongy urethra, the path of urine can take different routes. It might leak into the superficial perineal space, then flow into the loose tissue around the scrotum, penis, and upward, deep to the membrane layer in the lower belly. ● In the abdomen, it travels between the peritoneum and deep perineal pouch. Pelvic fractures can lead to a rupture in the urethra, causing urine and blood to enter the deep perineal pouch. ● In the perineum, urine enters the superficial perineal space, and the flow direction is influenced by the attachments of the perineal fascia. ● In the penis, urine enters the bulb and passes through the spongy urethra, which starts at the end of the intermediate part of the urethra and extends to the external urethral orifice. What are the boundaries of the ischioanal (ischiorectal) fossa? ● On the sides, it's shaped by the ischium and the lower part of the obturator internus muscle covered with obturator fascia. ● In the middle, the boundaries are set by the external anal sphincter muscle. The top part or roof is slanted and formed by the levator ani muscle as it comes down to join the sphincter. Both the external anal sphincter and the levator ani muscle wrap around the anal canal. ● At the back, the boundary is made by the sacrotuberous ligament and the gluteus maximus muscle. ● Towards the front, it's shaped by the pubic bones, specifically below where the puborectalis muscle starts. These parts of the fossa stretch upward into the urogenital triangle. On the worksheet The pudendal nerve and internal pudendal vessels can be found in the _________Pudendal__ canal which can be found in the lateral wall of the ischiorectal fossa. Branches of the pudendal nerve which are in or distal to the ischioanal fossa include: ______Inferior Rectal nerves. The inferior border of the anal valves forms the _________pectinate____line. Is it more painful to insert a needle above or below this line? Inserting a needle in this region is painless because the visceral afferent nerves that supply the anal canal are above this line. The anorectal junction is at the superior end of the anal columns__. Describe the vasculature and innervation of the scrotum (review!). Arteries 2 sets (anterior and posterior): The front of the scrotum is supplied from the: Femoral Artery —-> End branches of the external pudendal arteries—--> FRONTAL SCROTAL ARTERIES The back of the scrotum is supplied from the: End branches of the internal pudendal arteries—-->Perineal Artery—-> POSTERIOR SCROTAL ARTERIES ● It also receives branches from the CREMASTERIC ARTERIES which are branches of the inferior epigastric arteries. Veins: The veins run along side the arteries and drain into the EXTERNAL PUDENDAL VEINS Lymphatics: Lymph from the scrotum drain into the SUPERFICIAL INGUINAL LYMPH NODES Nerves: The front part is innervated by the ANTERIOR SCROTAL NERVES (from the ilio-inguinal nerve and by the genital branch of the genitofemoral nerve) The back part of the scrotum is innervated by the POSTERIOR SCROTAL NERVES (branches of the superficial perineal branches of the pundenal nerve and by the perineal branch of the branch of the posterior femoral cutaneous nerve) What are the root, body and glans of the penis? The root of the penis contains the crura and bulb and surrounded by the ischiocavernosus and bulbospongiosus muscles. The root is located in the superficial pouch of the perineal. The body is the free part that hangs from the pubic symphysis. Distinguish labia major and minor. The labia major are folds of the skin that is covered by the pudendal cleft which is the slit between the majora and indirectly provides protection for the urethral and vaginal orifices. Basically the bigger lips The labia minora are folds free of fat and hairless skin with a core of spongy connective tissue which contain erectile tissue as well as small blood vessels. Basically the thinner lips within the bigger lips. The erectile bodies of the penis/clitoris include 2 _____corpora cavernosa____ and 1 ______corpus spongiosum__. The corpus ________spongiosum__ expands distally to form the glans penis/clitoris. The corpora ____________cavernosa____ are continuous proximally with the crura of the penis/clitoris while the corpus ________spongiosum_____ is continuous proximally with the bulb of the penis/bulb of the vestibule. The bulb of the penis/vestibule is covered with _______________bulbospongiosus___ muscle, and the crura are covered with ______ischiocavernosus____ muscle. Distinguish erection, emission, ejaculation, and remission in terms of what happens at each stage and what innervation is responsible for each stage. Erection: During erection, parasympathetic stimulation by the cavernous nerves closes the arteriovenous anastomoses, allowing blood to fill the sinuses of the corpora of the penis. The bulbospongiosus and ischiocavernosus muscles contract, compressing the veins of the corpora cavernosa and impeding the return of venous blood. This results in the enlargement and rigidity of the erectile bodies, elevating the penis. Emission: During emission, peristalsis of the ductus deferentes and seminal glands delivers semen to the prostatic urethra through the ejaculatory ducts (see image). The smooth muscle in the prostate contracts, adding prostatic fluid to the seminal fluid. Emission is a sympathetic response mediated by the L1-L2 nerves. Ejaculation: Ejaculation occurs when semen is expelled from the urethra through the external urethral orifice. It is the result of the coordinated contraction of various muscles, including the bulbospongiosus muscles, which compress the urethra, and the external urethral sphincter, which relaxes to allow the passage of semen. Ejaculation is also a sympathetic response mediated by the L1-L2 nerves. Remission: After ejaculation, the penis gradually returns to a flaccid state during remission. This is due to sympathetic stimulation that opens the arteriovenous anastomoses, reducing blood inflow. The smooth muscle of the helicine arteries contracts, recoiling them and allowing more blood to be drained from the cavernous spaces into the deep dorsal vein. The bulbospongiosus and ischiocavernosus muscles relax, facilitating the drainage of blood from the erectile tissue. Describe the location of the greater and lesser vestibular glands. What is the function of these glands? Location of the Greater and Lesser Vestibular Glands: The greater vestibular glands, also known as Bartholin glands, are located on each side of the vestibule, posterolateral to the vaginal orifice. They are partly overlapped by the bulbs of the vestibule and surrounded by the bulbospongiosus muscles. The lesser vestibular glands (Skene’s glands - see image) are smaller glands that open into the vestibule between the urethral and vaginal orifices. Function of the Greater and Lesser Vestibular Glands: The greater vestibular glands secrete mucus into the vestibule during sexual arousal. This mucus helps lubricate the vaginal opening and moisten the labia and vestibule. The lesser vestibular glands also secrete mucus into the vestibule, contributing to the lubrication and moisture of the surrounding area. Why does a pudendal nerve block not anesthetize the anterior part of the perineum? A pudendal nerve block does not anesthetize the anterior part of the perineum because it is innervated by the ilio-inguinal nerve. The pudendal nerve block only anesthetizes most of the perineum, while the ilio-inguinal nerve block is required to abolish pain from the anterior part of the perineum. EXPLANATION: The perineum is the region between the anus and the external genitalia. The pudendal nerve is a major nerve that supplies sensation to the perineum. However, it's important to note that the anterior part of the perineum, which includes the front portion, is not completely anesthetized by a pudendal nerve block. In medical procedures or interventions where pain relief is necessary in the perineal area, a pudendal nerve block may be employed. However, since the ilio-inguinal nerve innervates the anterior part of the perineum, a pudendal nerve block alone may not provide complete anesthesia for this specific area. The ilio-inguinal nerve is responsible for supplying sensation to the upper part of the anterior perineum. To ensure comprehensive pain relief for the entire perineum, including the anterior part, an additional ilio-inguinal nerve block is required. This combined approach, using both pudendal and ilio-inguinal nerve blocks, helps to cover the sensory innervation of the entire perineal region during medical procedures or interventions. Here are some questions to guide your reading on the pelvis: ● What forms the walls and floor of the pelvis? What is the "true" vs. "false" pelvis. ● What is the sacral promontory? arcuate line? boundaries of the pelvic inlet and pelvic outlet? ● Study the bony anatomy of the pelvis. A lot of these terms are used to answer the next question. ● What are some shape differences between a male and female pelvis? The male and female pelvis differ in several shape characteristics. Here are the main differences: 1. General Structure: a. Male: The male pelvis is thick and heavy. b. Female: The female pelvis is thin and light. 2. Greater Pelvis (Pelvis Major): a. Male: The greater pelvis in males is deep. b. Female: The greater pelvis in females is shallow. 3. Lesser Pelvis (Pelvis Minor): a. Male: The lesser pelvis in males is narrow and deep. b. Female: The lesser pelvis in females is wide and shallow. 4. Pelvic Inlet (Superior Pelvic Aperture): a. Male: The pelvic inlet in males is heart-shaped. b. Female: The pelvic inlet in females is oval or rounded. 5. Pelvic Outlet (Inferior Pelvic Aperture): a. Male: The pelvic outlet in males is comparatively small. b. Female: The pelvic outlet in females is comparatively large. 6. Pubic Arch and Subpubic Angle: a. Male: The pubic arch and subpubic angle in males are narrow (<70 degrees). b. Female: The pubic arch and subpubic angle in females are wide (>80 degrees). 7. Obturator Foramen: a. Male: The obturator foramen in males is round. b. Female: The obturator foramen in females is oval. 8. Acetabulum: a. Male: The acetabulum in males is large. b. Female: The acetabulum in females is small. ● The joint between two pubic bones is the _____________________________. The joint between the sacrum and the ilium is supported by the anterior and posterior _____________________________ ligaments. Running from the sacrum to the the ischial tuberosity is a ligament called the ______________________________________. Running from the sacrum to the ischial spine is the ______________________________________ ligament. Together these ligaments define the greater and lesser sciatic notches and prevent the tendency of the lower sacrum to rotate superiorly under load. Answer: The joint between two pubic bones is the pubic symphysis. The joint between the sacrum and the ilium is supported by the anterior and posterior sacro-iliac ligaments. Running from the sacrum to the ischial tuberosity is a ligament called the sacrotuberous ligament. Running from the sacrum to the ischial spine is the sacrospinous ligament. Together these ligaments define the greater and lesser sciatic notches and prevent the tendency of the lower sacrum to rotate superiorly under load. ● What is the rectouterine pouch? The rectovesical pouch? The pararectal fossa? Rectouterine Pouch: The rectouterine pouch, also known as the pouch of Douglas, is a low point in the peritoneal cavity located between the rectum and the uterus in females. It is formed by the reflection of the peritoneum from the rectum to the posterior fornix of the vagina. The rectouterine pouch is an important anatomical landmark and can be palpated during rectal examination. Rectovesical Pouch: The rectovesical pouch is a low point in the peritoneal cavity located between the rectum and the bladder in males. It is formed by the reflection of the peritoneum from the rectum to the posterior wall of the bladder. The rectovesical pouch is also an important anatomical landmark and can be palpated during rectal examination. Pararectal Fossa: The pararectal fossa is a space on each side of the rectum that is formed by the lateral and posterior extension of the rectouterine or rectovesical pouch. It is located between the rectum and the pelvic sidewall. The pararectal fossa allows the rectum to distend as it fills with feces and can be palpated during rectal examination. ● ● How is the peritoneum related to the pelvic organs. The peritoneum covers the body and fundus of the uterus anteriorly and superiorly, but not the cervix. It is reflected anteriorly from the uterus onto the bladder and posteriorly over the posterior part of the fornix of the vagina onto the rectum. The peritoneum also forms folds and fossae as it reflects onto most of the pelvic viscera. ● What muscles compose the pelvic diaphragm? What is its function? ○ The muscles that compose the pelvic diaphragm are the levator ani and coccygeus muscles (the puborectalis, the pubococcygeus, and the iliococcygeus). ○ The levator ani muscles form the main part of the pelvic diaphragm, while the coccygeus muscles provide additional support. The pelvic diaphragm functions to support the pelvic organs, including the bladder, rectum, and uterus, and helps maintain continence. ○ The muscle forming the lateral wall of the pelvis is __________the obturator internus muscle. It covers and pads the lateral pelvic walls and converges posteriorly to attach to the femur. The obturator internus muscle is covered by the obturator fascia and provides attachment for the levator ani muscle______. ● The retropubic space is a potential space in the loose fatty endopelvic fascia that allows for the expansion of the ____urinary bladder___ as it fills. The ______rectorectal______ potential space does the same for the rectum ● Be able to identify the branches of the sacral plexus. Nerve to Piriformis: Innervates the piriformis muscle. Superior Gluteal Nerve: Supplies the gluteus medius, gluteus minimus, and tensor fasciae latae muscles. Inferior Gluteal Nerve: Innervates the gluteus maximus muscle. Sciatic Nerve: The largest nerve, it divides into the tibial nerve and common fibular (peroneal) nerve. The sciatic nerve provides motor and sensory innervation to the muscles and skin of the posterior thigh, leg, and foot. Posterior Femoral Cutaneous Nerve: Supplies the skin of the posterior thigh and leg. Pudendal Nerve: Innervates the perineum, including the muscles of the urogenital triangle, external anal sphincter, and the skin in the genital and anal regions.