Pelvic Cavity

Similarities/Differences between Male and Female Pelvis (pg. 331 – Moore)

Bony Pelvis Male FemaleGeneral Structure Thick and Heavy Thin and lightGreater Pelvis (false pelvis) Deep ShallowLesser Pelvis (true pelvis) Narrow and deep, tapering Wide and shallow, cylindricalPelvic inlet (superior pelvic aperture)

Heart-shaped, narrow Oval and rounded; wide

Pelvic outlet (inferior pelvic aperture)

Comparatively small Comparatively large

Pubic arch and subpubic angle Narrow (<70 degrees) Wide (>80 degrees)Obturator foramen Round OvalAcetabulum Large SmallGreater sciatic notch Narrow (-70 degrees) inverted V Almost 90 degrees

Musculature of the Pelvic Floor – Regions of the Levator ani (Gilroy- pg 140) (Moore- pg 339-342)

The pelvic floor is formed by the pelvic diaphragm, which consists of the levator ani and coccygeus muscles and the fascias covering the superior and inferior aspects of these muscles.

The Levator ani has three parts:

1. Puborectalis: the thicker, narrower, medial part of the levator ani2. Pubococcygeus: the wider but thinner intermediate part of the levator ani3. Iliococcygeus: the posterolateral part of the levator ani

Muscle Origin Insertion Innervation Blood Supply

Action

Levator ani

Puborectalis

Superior pubic ramus (both sides of pubic ramus)

Anococcygeal ligament

Direct branches of sacral plexus (S4),

Inferior gluteal a.

Pelvic diaphragm: supports pelvic

Pubococcygeus

Pubis (lateral to origin of puborectalis)

Anococcygeal ligament, coccyx

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inferior anal n.

viscera

Iliococcygeus

Internal obturator fascia of levator ani (tendinous arch)

Ischial spine

**An anterior gap between the medial borders of the levator ani muscles of each side—the urogenital hiatus—gives passage to the urethra and, in females, the vagina.

The levator ani is actively contracted during activities such as forced inspiration, coughing, sneezing, vomiting, and fixation of the trunk during strong movements of the upper limbs, primarily to increase support of the viscera during periods of increased intra-abdominal pressure.

Ligaments of the female reproductive system: Broad, Round, Ovarian, Suspensory, Cardinal (Transverse cervical) and Uterosacral (Gilroy p. 189, Moore p. 387)

o Broad Ligament: Double layer of peritoneum extending from the sides of the uterus that connects the sides of the uterus to the walls and floor of the pelvis.

Mesosalpinx- supports the uterine tube Mesovarium- attaches the ovary to the posterior aspect of the broad ligament Mesometrium- part of broad ligament that is below the attachment of the

mesovarium o Round Ligament: The function of the round ligament is maintenance of the anteversion

of the uterus (a position where the fundus of the uterus leans ventrally) during pregnancy. The round ligament leaves the pelvis via the deep inguinal ring, passes through the inguinal canal and continues on to the labia majora where its fibers spread and mix with the tissue of the mons pubis.

o Ovarian Ligament: located within the broad ligament that connects the ovary to the uterus

o Suspensory Ligament: a lateral extension of the broad ligament that attaches the ovary to the lateral pelvic wall. This peritoneal fold covers the ovarian vessels.

o Cardinal (Transverse cervical): extend from the supravaginal cervix and lateral parts of the fornix of the vagina to the lateral walls of the pelvis

o Uterosacral: pass superiorly and slightly posteriorly from the sides of the cervix to the middle of the sacrum; they are palpable during a rectal exam

Blood Supply to Urinary Bladder in Males and Females (Males: Sup./Inf. Vesical aa. Females: Sup. Vesical aa./ Branches from Vaginal aa. Both: Branches from the Obturator and Sup. Gluteal aa. (Moore pp. ???)

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o Blood Supply to Urinary Bladder in Males Umbilical a

Superior Vesical aa. Inferior Vesical aa. Small branches of obturator a. and inferior gluteal a.

o Blood Supply to Urinary Bladder in Females Umbilical a

Superior Vesical aa. Vaginal a Small branches of obturator a. and inferior gluteal a.

***These all branch from the Internal Iliac a.

The Arterial Supply of the Urinary Bladder

The main arteries supplying the bladder are branches of the internal iliac arteries. The superior vesicle artery, branches of the umbilical artery supply the

anterosuperior parts of the bladder. The inferior vesicle arteries (in males) or vaginal arteries (in females), branches of

the internal iliac arteries, supply the base of the bladder. The obturator and inferior gluteal arteries also supply small branches to the bladder.

Structures of the Spermatic Cord (re. Gilroy pp 206-8; table 2.6)o Begins at the scrotum near the post. border of the testes, travels through the inguinal

canal at the superficial inguinal ring (the medial entrance of the ring), and passes out at the deep inguinal ring (lateral entrance of the ring) heading into the pelvic cavity.

o Fascia coverings from superficial to deep are the external spermatic fascia, cremasteric fascia (with cremasteric muscle), and the internal spermatic fascia. Within the cremasteric fascia are loops of muscle fibers of the cremasteric muscle. It functions to draw the testis up near the body during contraction and releasing them when relaxed. This is done in response to temperature; the testis must be maintained at approximately one degree Celsius cooler than the body to regulate spermatogenesis. The cremaster muscle is innervated by the genital branch of the genitofemoral n. (L1, L2). A synergist of the cremaster is the dartos muscle which overlies the external spermatic fascia. The difference is that the cremaster muscle is smooth muscle receiving somatic impulses and the dartos muscle is striated receiving parasympathetic impulses.

o Deep to the internal spermatic fascia lie the ductus deferens, the testicular a., the artery of the ductus deferens, the cremasteric a., the pampiniform plexus, the nerves of both

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types of fibers mentioned earlier, lymphatic vessels and the vaginalis coverings of the testes (tunica vaginalis).

Regions of the Male Urethra (re. Gilroy p 368; fig 3.30 b; table 3.6) Beginning at the urinary bladder the first part of the male urethra is the prostatic urethra.

This part has several openings for the incoming seminal vesicles from the ductus deferens. After the prostatic urethra is the membranous urethra. Just distal in this part of the male

urethra are the openings for the bulbourethral glands which add their contents to the seminal fluid.

The remainder of the male urethra is called the spongy urethra.

Parasympathetic/Pelvic splanchnic nerves = innervation source for both male and female vasodilation of erectile tissues (penis and clitoris) (re. Gilroy p360, 380, 389, 423, 425; ff. 3.21, 22, 23, 47) Arise from ant. rami of spinal nerve S2-S4 (keep your junk off the floor). In males the fibers travel to the erectile tissues of the penis. It does this by allowing

straightening of the helicine aa. of the penis which begin to engorge the tissue with blood. Parasympathetic stimulation also serves to contract the urethral and bulbospongiosus muscles

In females the path and function are a bit more complicated. The sympathetic and parasympathetic fibers join at the hypogastric-uterovaginal plexus. Sensation in the uterus is transported by sympathetic fibers. Sensation from the cervix and vagina follows a parasympathetic pathway. NOT MENTIONED DIRECTLY BY GILROY, it can be assumed that sensation of the female external genitalia (clitoris, glands of the vestibule) are carried by parasympathetic fibers of the pelvic spanchnic nn.

Anatomical Regions of Fallopian Tubes/Uterus (Infundibulum; Fimbriae; Ampulla; Isthmus; Uterine Part AND Fundus and Body of UterusInternal/External Os of Cervix (2 Questions) [Moore p. 383-387]

1. Uterine tubes - aka oviducts or fallopian tubes; lie in narrow mesentery (mesosalpinx) and form the superior edges of the broad ligaments; divided into four parts:

a. Infundibulum - funnel shaped distal end that opens into the peritoneal cavity through the abdominal ostium.The most distal portion the infund. are the fimbraie that spread over the medial surface of the ovary; one large ovarian fimbrae reaches to the superior pole of the ovary.

b. Ampulla - the widest and longest portion of the fallopian tubes. it begins at the medial end of infundibulum;this is the site where fertilization of the oocyte usually occurs.

c. Isthmus - the thick part of the tube that enters the uterine horn.d. Uterine part - the short intramural portion of the tube that passes the uterine wall and

opens via that uterine ostium into the uterine cavity at the uterine horn.

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2. Body - forms the superior 2/3 of the organ and includes the fundus (rounded portion lying superior to uterine ostia)

a. The body lies between the layers of broad ligament, is freely movable, and has two parts: vesical (r/t bladder) and intestinal. The isthmus of the uterus (~1cm long) demarcates the uterus from the cervix.

3. External Os - is the portion of the cervix inferior to the cervical canal that extends into the vagina; the os is surrounded by the "vaginal part" of the cervix, which is then surrounded by the vaginal fornix.

4. Internal Os - is the segment superior to the cervical canal; it is a narrowing inside the isthmus of the uterine body.

5. Cervical cavity: external os --> cervical canal --> internal os --> fundus6. BS: arterial

a. lateral aspects - ovarian aa. from AA.b. medial aspects - uterine aa. from internal iliac (which bifurcate into tubal and ovarian

that anastamose).7. BS: venous

a. panpiniform plexus merges into ovarian vein: right drains to IVC, and left drains to renal v. then IVC.

8. Inn: T11-L1 spinal sensory; parasympathetic from S2-4 pelvic splanchnic nn. and inferior hypogastric plexus.

9. BS of uterus: uterine arteries from the internal iliac; the uterine veins travel to the iliac veins and to the IVC

o Inn of uterus: parasympathetic from pelvic splanchnic (S2-4) & sensory (T10-12)

Layers of the Uterine Wall [Moore p. 385-386]o The Wall of the Body is three layers (coats) deep:

perimetrium - serous outer coat; peritoneum supported by connective tissue myometrium - middle coat; distended during pregnancy; houses main branches of

blood vessels and nerves. dilates the cerval os to expel fetus; myometrial contractions produce cramping

endometrium - innermost coat; firmly attached to myometrium; active layer during menstruation; blastocyst implants in this layer during implantation; this layer sheds if implantation does not occur.

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Anatomy of the Penis: Corpora cavernosa, Corpus spongiosum, deep dorsal artery and vein of the penis, penile/spongy urethra [Moore p. 419]

Penis- the male organ of copulation consists of three cavernous bodies of erectile tissue:

o Corpora Cavernosa - the dorsal layer, (when the penis is in anatomical position (erect)-the dorsum is anterior);

o Corpora Spongiosum - the ventral layero Each corporus layer has an outer fibrous tunica albuginea;o Superficial to the outer covering is the deep fascia of the penis (Buck fascia), which is the

continuation of the deep perineal fascia that forms a membranous covering over the cavernosa and spongiosa to bind them together.

o The c. cavernosum fuse together in the median plane, except posteriorly where they seperate to form the crura of the penis; internally the cavernous tissue is separated by the septum penis.

o The spongy urethra [Moore p. 369, 406 418; Fig 3.60] – begins at distal intermediate part of urethra (the bulbourethral gland opens into the bulbous part to form the intrabulbar fossa) and ends at the ext. urethral orifice and widens at the navicular fossa.

o Arterial supply of penis [Moore p. 421-422]: the penis is supplied mainly by branches of the pudendal aa.

Dorsal aa : run on either side of the deep dorsal vein of the penis in the dorsal groove between the corp. cavernosa to supply the fibrous tissue around the corp. cav., corp. spong., spongy urethra, and penile tissue

Deep dorsal vv : located in the deep fascia and joined by a venous plexus that drains blood from the cavernous spaces. The vein passes between laminae of the suspensory ligament of the penis, inferior to pubic ligament and anterior to perineal membrane, to enter the pelvis and drain into the prostatic venous plexus.

Skin and subcutaneous tissue of the penis : drains into the superficial dorsal v. and then to the superficial external pudendal v.

Perineal muscles: Ischiocavernosus and bulbospongiosus mus. [Moore p. 423]o The roots of the penis (attached part) consist of the crura and the ischiocavernosus and

bulbospongiosus muscles.o The bulbospongiosus muscle compresses the bulb of the penis and the c. sponigosum to aid

in emptying urine and semen. The anterior fibers encircle the proximal body of the penis and assist in erection by increasing pressure on erectile tissue in the root of the penis. They also compress the deep dorsal vein and help promote enlarge the penis.

o The ischiocavernous muscles surround the crura in root penis and forces blood from the cavernous spaces in the crura in the distal parts of the c. cavernosa and increases turgidity;

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contraction of this muscle compresses the deep dorsal vein to restrict venous outflow to maintain erection.

Female External Genitalia; Mons pubis, labia majora, labia minora, vestibule, vestibular glands, glans,clitoris, external urethral orifice, vafinal orifice Refer to pages 192-193 in the Gilroy for better pictures of these structures. Also refer to

pages 461-464 in the Moore. From the way the bullet is worded I think we will just have to ID these structures on the exam so be familiar with figures 14.12, 14.13, and 14.14 in Gilroy! However, I have provided definitions of the terms below. The picture below is from Dr. Peterson’s ppt.

Mons Pubis – rounded, fatty eminence anterior to the pubic symphysis. After puberty it is covered with coarse pubic hairs.

Labia Majora – prominent folds of skin that provide protection for the urethral and vaginal orifices.

Labia Minora – rounded folds of fat-free, hairless skin. They are enclosed in the pudendal cleft and surround the vestibule.

Vestibule – the space surrounded by the labia minora into which the orifices of the urethra and vagina and the ducts of the greater and lesser vestibular glands open.

Vestibular glands – the greater vestibular glands (bartholins glands) are located on either side of the vestibule and are partly surrounded by bulbospongiosus muscles. The glands secrete mucus into the vestibule during sexual arousal. The lesser vestibular glands secrete mucus into the vestibule, which moistens the labia and vestibule.

Glans – part of the clitoris that is covered by a prepuce and is the most highly innervated part of the clitoris. Functions as an organ of sexual arousal.

Clitoris – an erectile organ located where the labia minora meet anteriorly. Consists of a root and a body; which are composed of two crura; two corpora cavernosa; and the glans of the clitoris.

External urethral orifice – located posteroinferior to the glans of the clitoris and anterior to the vaginal orifice. Paraurethral glands are locate on either side of the orifice.

External anatomy of penis/scrotum: penile raphe, scrotal raphe, glans penis, corona of glans penis, present in uncircumcised males prepuce, frenulum of prepuce Prepuce, and frenulum of the prepuce (this photo can be better seen on page 454 of the

Moore). Other photos of male external genitalia can be found on pages 196-199 of the Gilroy.

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Nerves of the penis : deep dorsal nerve (from the pudendal nerve = sensory and sympathetic fibers), ilioinguinal nerve, cavernous nerves (from pelvic splanchnic nerves = parasympathetic fibers) The nerves derive from the S2-S4 spinal cord segments and spinal ganglia, passing through

the pelvic splanchnic and pudendal nerves respectively.

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Sensory and sympathetic innervation is provided by the DORSAL NERVE OF THE PENIS which is a terminal branch of the PUDENDAL NERVE. It runs to the dorsum of the penis, where it runs lateral to the dorsal artery. The DORSAL NERVE supplies the SKIN and GLANS of the penis.

Branches of the ILIOINGUINAL NERVE supply the SKIN AT THE ROOT OF THE PENIS. CAVERNOUS NERVES conveying parasympathetic fibers (independent from the prostatic

nerve plexus) innervate the HELICINE ARTERIES OF THE ERECTILE TISSUE.

1. Name the organs that comprise the hindgut.2.

- Distal ½ of the transverse colon, descending colon, sigmoid colon, and rectum 2. Identify the vessels that supply blood to the rectum and the arteries from which they originate.

- Superior rectal artery - from the Inferior mesenteric artery- Middle rectal artery - from the internal iliac artery- Inferior rectal artery - from the internal pudendal artery, which is a branch of the internal iliac artery

 3. Locate the following on the model of the torso:

- Splenic flexure- Haustra- Taenia libra- Epiploic appendages

 4. The sigmoid colon is located on the posterior wall of the lower abdominal wall, and upper region

of the pelvic cavity. So why is it considered a portion of the hind gut, and not retroperitoneal?- The sigmoid colon is completely covered by the peritoneum, and thus is part of the hind gut

 5. The hind gut is innervated by two sets of nerves. What are they, and what type of innervation do they supply?

- The lumbar splanchnic nerves provide sympathetic innervation- The pelvic splanchnic nerves provide parasympathetic innervation

6. Distinguish between male and female iterations of the internal iliac artery and its branches. Be sure to list the arteries, and differentiate between those arteries that are considered parietal and those that are visceral.

- There are five parietal (those supplying the pelvic wall) and four visceral (those supplying the pelvic organs)

Branches of the Internal Iliac Artery – Males Iliolumbar artery Superior Gluteal artery Lateral Sacral artery Umbilical artery

o Artery to the ductus deferenso Superior Vesical artery

Obturator artery Inferior Vesical artery Middle Rectal artery Internal Pudendal artery

o Inferior Rectal artery Inferior Gluteal artery

Branches of the Internal Iliac Artery – Females

Iliolumbar artery Superior Gluteal artery Lateral Sacral artery

Umbilical arteryo Superior Vesical artery

Obturator artery Middle Rectal artery Uterine artery (w/ or w/o vaginal branch)

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Vaginal artery (depends on above) Internal Pudendal artery

o Inferior Rectal artery Inferior Gluteal artery

7. What branches of the internal iliac supply the urinary bladder? Note the differences between males and females.

- Males: superior and inferior vesical arteries, umbilical artery- Females: superior vesical artery, umbilical artery, vaginal artery

8. Name the branches of the posterior division of the internal iliac artery and their muscular targets.

- Iliolumbar artery – psoas major, quadratus lumborum- Superior gluteal artery – gluteus major, medius, minor, TFL- Lateral sacral artery – piriformis

9. Name the three arterial branches that supply the adrenal glands and describe where they come from.

- Superior suprarenal artery – from the inferior phrenic artery- Middle suprarenal artery – from the abdominal aorta- Inferior suprarenal artery – from the renal artery.

10. Distinguish between the locations of the gastric and gastro-omental arteries and identify the arteries from which they originate.

- The gastric arteries travel along the lesser curvature of the stomach, whereas the gastro-omental arteries travel along the greater curvature of the stomach. The right gastric artery originates from the common hepatic artery. The left gastric artery is a branch of the celiac trunk. The right gastro-omental artery branches from the gastroduodenal artery. The left gastro-omental artery is a branch of the splenic artery.

11. Describe the branching of the celiac trunk.- Common hepatic artery

- Right gastric artery- Gastroduodenal artery

- Right gastro-omental artery- Superior pancreaticoduodenal artery

- Anterior & posterior branches- Proper hepatic artery

- Left hepatic artery- Right hepatic artery

- Cystic artery- Splenic artery

- Left gastro-omental artery- Short gastric arteries- Posterior gastric artery- Pancreatic branches

- Left gastric artery

12. How many lumbar arteries originate from abdominal aorta?- Eight, as four bilateral pairs

13. Identify the primary branches of the superior mesenteric artery?- Inferior pancreaticoduodenal artery 

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- Middle colic artery- Right colic artery- Ileocolic artery- Intestinal arteries

14. What are the three branches of the inferior mesenteric artery?- Left colic artery, sigmoid artery, superior rectal artery

15. Scarpa's fascia is continuous with what structure in the pelvic region?        - Scarpa's fascia is continuous with the dartos layer of the scrotum

16. Identify and demonstrate the actions of the internal and external oblique muscles.- Unilateral - bends trunk to the same side, rotates trunk to opposite side.- Bilateral - Flexes trunk, compresses abdomen, and stabilizes pelvis

17. List the contents of the inguinal canal, being sure to distinguish between males and females.- Males: spermatic cord, ilioinguinal n., blood vessels and lymphatic vessels- Females: round ligament of the uterus, ilioinguinal n., blood vessels and lymphatic vessels

18. Describe the boundaries of the inguinal canal.- Anterior wall: external oblique aponeurosis- Roof: arching fibers of the internal oblique and the transversus abdominis- Floor: inguinal ligament- Posterior wall: transversalis fascia and parietal peritoneum

19.  List from superficial to deep the layers of the abdominal wall at a point just lateral to the linea alba and superior to the arcuate line.

- Skin, Camper's fascia, Scarpa's fascia, external oblique aponeurosis, internal oblique aponeurosis, rectus abdominis, rectus sheath/transversus abdominis aponeurosis, peritoneum.

20. Define “portal system” as it pertains to anatomy, and identify the three portal systems of the human body.

- A portal system is composed of two capillary beds connected by a portal vein that transport relatively high concentrations of products from one region directly to another region without passing through the heart. The three portal systems of the human body are the Hepatic portal system of the liver, the hypophyseal portal system of the anterior pituitary gland, and the renal portal system of the kidney.

21. Describe the hepatic portal system.- In systemic circulation, venous blood passing through spleen, pancreas, stomach, and intestines is not

carried directly to heart. It passes through hepatic portal vein to the Liver. Vein begins as capillaries from visceral organs and ends in the liver again as capillaries. These capillaries converge to form the hepatic vein, which joins the inferior vena cava.

22. What are the specialized blood vessels of the secondary capillary bed of the hepatic portal system called and what vein do they collectively attach to.

- The vessels of the secondary capillary bed of the hepatic portal system are called hepatic sinusoids and they travel between the hepatocytes to attach to the central vein, which connects to the hepatic vein.

23. Describe the blood in the hepatic portal vein and in the hepatic sinusoids.- The blood in the hepatic portal vein is nutrient-rich and partially deoxygenated (but contains

approximately 40% more oxygen than systemic deoxygenated blood returning to the heart). Once that blood reaches the hepatic sinusoids, it is mixed with arterial blood from the hepatic artery.

24. Identify the following features of the uterus on a model: body, fundus, isthmus, cervix. - Body- part between the fundus and cervix - Fundus- rounded part of the body that lies superior to the attachments of the uterine tubes - Isthmus- portion of body which is superior to the cervix - Cervix- portion of uterus that protrudes into the vaginal canal

25. Name the vessel that supplies blood to the vagina and identify the structure that passes between it and the uterine artery (the location of this structure must be identified during a hysterectomy).

- Vaginal artery (or vaginal branch of uterine artery)- Ureter

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26. Identify the three distinct areas of the broad ligament and the location each. - Mesosalpinx: supports the uterine tube - Mesovarium: attaches the ovary to the posterior aspect of the broad ligament - Mesometrium: part of broad ligament that is below the attachment of the mesovarium

27. Identify two ligaments of the ovaries and locate them on the donor (if your donor does not contain them, describe their location instead).

- Ovarian ligament: within the broad ligament that connects the ovary to the uterus - Suspensory ligament of the ovary: peritoneal fold that covers the ovarian vessels/ it extends into the

greater pelvis from the superior aspect of the pelvis

28. Name the contents of the superficial perineal pouch in the female. - Ischiocavernosus, bulbospongiosus, superficial transverse perineal - Crus of the clitoris - Bulb of the vestibule - Greater vestibular gland

29. Identify the two erectile tissues of the penis.- Corpora cavernosa (paired), corpus spongiosum

30. Identify the blood vessels of the testicle and the reason for their respective position in space.- Testicular artery, pampiniform plexus- The close proximity of the pampiniform plexus is and the testicular artery allows heat to pass from the

artery to the veins so that the deoxygenated blood is returned to body temperature

31. Describe the path of sperm from the testicle to the urethra.- Testicle, epididymis, ductus deferens, seminal vesicles, prostatic urethra, membranous urethra, penile

(spongy) urethra

32. Trace the flow of blood from the heart to the erectile tissue of the penis.- Aorta, common iliac artery, internal iliac artery, internal pudendal artery, deep dorsal artery of the

penis, helicine arteries

33. Name the layers of the scrotal sac from superficial to deep.- Scrotal skin, tunica darts, external spermatic fascia, cremaster muscle, internal spermatic fascia,

tunica vaginalis (parietal layer), tunica vaginalis (visceral layer).

34. What specific organs comprise the foregut?- Stomach, pancreas, duodenum, liver, gallbladder, spleen

35. What structures, primarily composed of adipose, are associated with the greater and lesser curvatures of the stomach? Describe their function.

- Greater curvature: greater omentum- Lesser curvature: lesser omentum- The greater and lesser omenta function structurally as "shock absorbers" that surround and protect the

abdominal viscera from physical injury. The omenta also function as insulators, protecting the organs from temperature change.

36. Describe the flow of bile (beginning with its production in the liver and ending in the duodenum).

- Liver(production of Bile) Right and Left Hepatic Duct Common Hepatic Duct Cystic Duct Gallbladder (storage until needed) Cystic Duct Common Bile Duct (joining with the main pancreatic duct) Sphincter of Oddi Duodenum

37. Describe the parasympathetic innervation pathways for organs of the foregut, midgut, and hindgut.

- Organs of the foregut and midgut are innervated by preganglionic neurons whose axons comprise CN X – the vagus nerve. The post ganglionic neurons are embedded in the walls of these foregut and midgut organs in the submucosal plexus (innervation source for glands) and the myenteric plexus (innervation source for smooth muscle peristalsis). Organs of the hindgut are innervated by preganglionic neurons whose axons comprise the pelvic splanchnic nerves (S2, 3, 4). The post ganglionic neurons are embedded in the walls of these hindgut organs in the submucosal plexus (innervation source for glands) and the myenteric plexus (innervation source for smooth muscle peristalsis).

38. Describe the anatomical role the thoracic splanchnic nerves have in a sympathetic response.- There are three thoracic splanchic nerves:

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- The Greater thoracic splanchnic nerve (ventral rami of T5 – T9) is comprised of pre-ganglionic axons that synapse with post-ganglionic neurons in the celiac ganglion. The post-ganglionic axons comprise the celiac plexus and innervate foregut organs – resulting in peristaltic inhibition and vasoconstriction of blood vessels. In addition, the Greater splanchnic nerveCeliac ganglion innervates the adrenal medulla where the chromaffin cells of the medulla the actual post-synaptic neurons. When stimulated these cells release epinephrine and norepinephrine into the blood stream.

- The Lesser thoracic splanchnic nerve (ventral rami of T10 – T11) is comprised of pre-ganglionic axons that synapse with post-ganglionic neurons in the aorticorenal ganglia and the superior mesenteric ganglion. The post-ganglionic axons innervate midgut organs and kidney – resulting in peristaltic inhibition and vasoconstriction of blood vessels.

- The Least thoracic splanchnic nerve (ventral rami of T12) is comprised of pre-ganglionic axons that synapse with post-ganglionic neurons in the aorticorenal ganglion. The post-ganglionic axons comprise the celiac plexus and innervate kidneys, ureters– resulting in inhibition of peristalsis of urine flow to bladder and vasoconstriction of renal blood vessels.

39. Describe the role of the lumbar splanchnic nerves.- The Lumbar splanchnic nerve (ventral rami of L1 – L3) is comprised of preganglionic axons that

synapse with post-ganglionic neurons in the Inferior mesenteric ganglion. The axons of the post-ganglionic neurons terminate on the smooth muscle layer of the distal transverse colon and descending colon inhibiting peristalsis. Post-ganglionic axons of L1 and L2 transmit inhibitory impulses to the bladder and internal urethral sphincter.

- The lumbar splanchnic nerve (ventral rami of L4 – L5) is comprised of preganglionic axons that do NOT synapse in a ganglion – instead they synapse in the hypogastric plexus. The post-ganglionic axons travel to the smooth muscle layer of the sigmoid colon, rectum inhibiting peristalsis. The post-ganglionic axons also travel to the prostate and seminal vesicles/bulb of the vestibule and Greater vestibular glands. During sexual arousal sympathetic impulses induce glandular secretion.

40. Describe the role of the sacral splanchnic nerves.- The sacral splanchnic nerves (S1 – S3) are comprised of preganglionic axons that do NOT synapse in a

ganglion – instead they synapse in the hypogastric plexus. The postganglionic axons travel to reproductive organs and external genitalia inducing smooth muscle contraction, skeletal muscle contraction (bulbospongiosus muscle) and glandular secretion during sexual climax.

41. Describe the role of the Pudendal nerves in both men and women.- The Pudenal nerves (ventral rami of S2,3,4) relay both sensory impulses and motor impulses.

Transmission of impulses generated by tactile stimulation of the external genitalia is relayed to the spinal cord via the pudendal nerves in both men and women. In addition, the pudendal nerve transmits efferent motor impulses to the external anal and external urethral sphincters to inhibit sphincter relaxation.

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