this lecture describes the development of the gut tube starting from the infolding of the yolk sac in the development and positioning of the different sections of the intestines and stomach. early development: the epithelium and mucosa are derived from the endoderm layer while the muscularis is derived from the mesoderm layer. the gut tube is surrounded by two peritoneal sacs that form the visceral and parietal peritoneum. the dorsal mesogastrium is the section of the peritoneum early in development that connects the gut tube to the posterior abdominal wall. the greater omentum is part of the peritoneal layer that folds down over the intestines and serves as a repository for visceral fat (as well as having an active role in the immune system). the mesentary is the portion of the dorsal mesogastrium that attaches to the posterior gut tube and contains neurovascular bundles within its layers.
the gut tube itself undergoes several revolutions and many convolutions during its development, starting with a 90 degree rotation that positions the stomach to the left and the liver to the right of the abdominal cavity. the midgut then herniates and forms a U shaped loop in the 6th week, within which the small intestine develops. the formation of this long section of gut tube causes a bulging of the tube into the vitelline duct (?) and a subsequent entry into the abdominal cavity. the order of re-entry determines whether the section of the gut tube is classified as retroperitoneal or intraperitoneal-- retroperitoneal sections are affixed to the posterior abdominal wall and includes the duodenum, ascending, and descending colons. intraperitoneal are loosely suspended by mesentary and includes the small intestine and transverse colon. if the abdominal cavity closes before reentry of the gut tube is complete, this can result in a persistent vitelline duct, which might lead to such pathologies as vitelline cyst, vitelline fistula, or diverticulosis.
the gut tube is divided into three sections: foregut, midgut, hindgut. each section corresponds to multiple sections of the GI tract as we know it and also corresponds to a different major artery. for example, the foregut includes the stomach and duodenum and has blood supplied by the celiac artery. the midgut includes the jejunum, ileum, and ascending/transverse large intestine, and has blood supplied by the superior mesenteric artery. the hindgut includes the transverse and descending large intestine, rectum, and anal canal. as mentioned before, the mesentery that suspends the small intestine contains neurovascular bundles within its folds; there are two types of arteries that supply blood to the gut- vasa recta and arcade arteries. vasa recta arteries are more prevalent in the jejunum, arcades in the ileum.
sympathetic activity can constrict arteries, either in response to stress or a drop in blood pressure and activation of the RAAS system, decreasing blood and oxygen flow to the intestinal mucosa. eventually, the autoregulatory escape mechanism kicks in and brings the blood pressure in the intestines back to normal even with continued sympathetic activity. the sympathetic response to stress can ultimately result in toxemia due to the weakened epithelial wall (because of reduced oxygen flow) allowing in more microorganisms and toxins. this same result can come about due to ischemia caused by decreased cardiac output or decreased blood pressure as well.
questions
basic structures...
1. what is the gut tube made from? when does it start to develop?
2. the epithelium and mucosa of the gut tube are derived from...
3. smooth muscle is derived from...
4. describe the origin of the peritoneum.
5. what is the dorsal mesogastrium? what does it form?
6. what is the greater omentum? what are some of its properties?
7. spleen splits the greater omentum into...
8. describe the formation of the mesentery.
9. what travels between the layers of mesentery?
rotation and differentiation...
10. describe what happens in peritoneal rotation.
11. how does the large intestine come to surround the small intestine?
12. what does it mean for a section of the gut tube to be retroperitoneal and what is an example?
13. what does it mean for a section of the gut tube to be intraperitoneal and what is an example?
14. what determines whether a section of the gut tube will be retroperitoneal vs. intraperitoneal?
15. what is a persistent vitelline duct and what pathologies can it result in?
16. what is omphalocoele?
gut divisions and blood supply...
17. which arteries define the three sections of the GI tract?
18. what does the foregut form?
19. what does the midgut form?
20. what does the hindgut form?
21. which branches of the superior mesenteric artery supply the jejunum and ileum?
22. which branches of the superior mesenteric artery supply the ascending and transverse colon?
23. what are the two types of arteries that branch off and anastamose in the jejunum and ileum?
24. sympathetics constrict arteries in response to...
25. what is autoregulatory escape?
26. what are the two ways in which ischemia of the gut can occur?
27. how can toxemia result from ischemia of the gut?
answers
1. from the yolk sac during the 4th week.
2. endoderm
3. mesoderm
4. during the 5th and 6th weeks, two peritoneal sacs press against either side of the liver and stomach and form the visceral and parietal peritoneum.
5. the dorsal section of the peritoneal fold- forms the greater omentum and mesentery.
6. part of the dorsal mesogastrium that folds down over the intestine and is a repository for visceral fat. also has strong immune stimulating properties.
7. gastrolienal and lienorenal ligaments.
8. mesentary is formed from the portion of the dorsal mesogastrium that is attached to the posterior wall of the stomach.
9. neurovascular bundles to the visceral organs.
10. due to the 90 degree rotation of the peritoneal cavity, the stomach ends up to the left and the liver to the right (whereas they were both in the center before)
11. the midgut "herniates" and forms a U shaped loop during the 6th week, rotating 270 degrees around the superior mesenteric artery.
12. the portions that are affixed to the posterior wall of the abdominal wall and partially covered by peritoneum: examples are the ascending and descending large instestine and the duodenum.
13. the portion that is surrounded by the visceral peritoneum and is relatively mobile, suspended by mesentary. example is the small intestine and transverse colon.
14. the order of "reentry" into the abdominal cavity.
15. the vestiges of the vitelline duct which can result in a connection between the ileum and abdominal wall- potentially causing meckel's diverticulum, vitelline cyst, or a vitelline fistula.
16. a section of intestine trapped by early closing of the abdominal cavity before full retraction.
17. celiac artery: foregut, superior mesenteric: midgut, inferior mesenteric: hindgut.
18. stomach, duodenum
19. jejunum, ileum, proximal large intestine (ascending and transverse)
20. transverse, descending, sigmoid large intestine, rectum, anal canal.
21. sequential branches
22. ileocolic, right and middle colic arteries.
23. vasa recta in jejunum, arcades in ileum.
24. exercise or a drop in blood pressure
25. a compensatory mechanism which will allow vasodilation to offset excess sympathetic activity.
26. either by occlusion of the mesenteric arteries or decreased cardiac output/continuous vasoconstriction.
27. toxemia can develop by bacterial / toxin entry into intestinal epithelium which might occur when oxygen flow to the mucosa is decreased because blood flow is decreased (oxygen diffuses from arterioles to venules rather than to mucosa)
Showing posts with label embryology. Show all posts
Showing posts with label embryology. Show all posts
Wednesday, March 11, 2009
Tuesday, February 10, 2009
organ systems: reproductive anatomy and embryology
this lecture covered the anatomy and embryology of the male and female reproductive systems, first introduced in histology last semester. first it went through basic anatomical features of the female reproductive system. at the end of the vagina is the cervix, which is the opening to the uterus (the areas beside the cervix are called "fornices"). the uterus has four sections, the cervix, isthmus, body, and fundus. the uterine tubes branch off of the uterus and are divided into section as well: isthmus, ampula (where fertilization takes place), infundibulum, ending in the fimbria which open up into the peritoneal cavity. the uterus itself can be tilted forward, called anteversion, and additionally bent forward, called anteflexion. it is held in place by the round ligament, the uterosacral ligament, and the transverse sacral ligament. the ovaries are held in place by suspensory and ovarian ligaments.
the male reproductive anatomy basically follows spermatogenesis as it begins in the testes and ends at the penis. spermatogenesis occurs in the seminiferous tubules of the testis, aided by sertoli cells and leydig cells (which secrete testosterone). the spermatogonia in the walls of the tubules develop into spermatocytes, into spermatids, into spermatozoans, which are then released from the tubules. they travel into the rete testis, and into the ductus epididymus, which is a 4-5m long highly coiled tube where spermatozoans mature. from there they travel up the ductus deferens, which goes through the inguinal canal and behind the bladder, encountering the first of the ducts which combine with sperm to create seminal fluid.
the first of these is the seminal vesicles, which secrete a whitish viscous fluid containing fructose (recall the polyol pathway from biochemistry, and how sperm cells use fructose instead of glucose for metabolism). next is the ejaculatory ducts, which meet the urethra at the urethric crest of the prostate. next is the prostatic ducts in the prostate. finally, the bulbourethral gland is embedded in the external urethral sphincter and lubricates the penile urethra as well as neutralizing acidity from the urine.
some homologies of external genitalia between males and females are discussed: the penis and clitoris are both formed from the "genital tubercle". the "labiascrotal swelling" forms the scrotum in males and the labia majora in females. the urethral folds forms the urethra in males and the labia minora in females.
next we discuss the embryology of the reproductive systems. male/female differentiation begins around 4 weeks during development. before this point, germ cells in both sexes migrate from the yolk sac to the sex cords, forming the precursor to the gonads. in males, the mesonephric ducts (wolffian) develop while the paramesonephric (mullerian) ultimately degrade. the mesonephric ducts form the efferent ductules, ductus deferens, seminiferous tubules, and ejaculatory ducts.
in females, the follicles (recall the anatomy from the histology lecture) are formed by sex cords which form cortical cords, which form follicles. inside the follicles are oogonia, which began forming and dividing from the germ cells that migrated from the yolk sac. as mentioned above, the mesonephric duct eventually disappears and the paramesonephric duct develops into the female reproductive anatomy: the top of the ducts form the uterine tubes, ending in the infundibulum, and the bottom of the ducts form the uterus and vagina. the sinovaginal bulb is formed by the fusion of the urogenital sinus and the paramesonephric ducts, and the opening to the vagina forms by the hollowing out of the sinovaginal bulb.
some pathologies in development: hypospadias is the opening of the urethra in the ventral side of the penis instead of at the glans. chryptorchism is incomplete descent of the testis due to abnormal androgen production. congenital inguinal hernia is when the intestines come through the inguinal canal into the scrotal area. hydrocele is the acculumulation of fluid in the tunica vaginalis, which covers the testis.
questions
anatomy...
1. greater and lesser pelvis separated by...
2. what is the pelvic diaphragm made of?
3. what are the four parts of the uterus?
4. what are anteversion and anteflexion?
5. what is the connective tissue that holds the uterus?
6. what are the sections of the uterine tube?
7. what is the ovary held in place by?
8. what is the broad ligament formed from?
9. what are the fornices?
10. what is the tunica albuginea?
11. leydig cells secrete...
12. sertoli cells support...
13. describe spermatogenesis. (not on test)
14. describe the pathway of the sperm out from the seminiferous tubules to the ductus deferens.
15. describe the epididymus.
16. ductus deferens transports sperm cells through...
17. what do the seminal vescicles do?
18. where do the ejaculatory ducts open into the urethra?
19. prostate gland secrete into urethra via...
20. where is the bulbourethral gland? what does it do (2)?
21. what forms the seminal fluid?
22. what are the layers to the prostate?
23. what are the zones of the prostate?
24. what zones does hypertrophy of the prostate affect?
25. what zones does prostate cancer affect?
26. what does the prostate gland secrete? (4)
26b. what is an indicator for prostate cancer?
27. where is the superficial inguinal ring?
28. where is the deep inguinal ring?
29. conjoint tendon is the lowest part of...
30a. describe the path of the spermatic cord.
30b. what is the equivalent of the spermatic cord in the female and where does it pass through?
31. what is the pampiniform plexus?
32. what is the cremaster muscle?
33. what is an inguinal hernia?
34. what is the difference between a direct and indirect inguinal hernia?
what is the analogous erectile tissue on the female:
35. penis
36. corpus cavernosum
37. corpus spongiosum
38. bulb of penis and glans penis
39. what is it that imparts turgidity during an erection?
40. describe the corpus spongiosum.
41. describe the general purpose of the ischiocavernous muscle in males and females.
42. describe the general purpose of the bulbospongiosus muscle in males and females.
43. describe the general purpose of the transverse perinei muscle in males and females.
44. what gland on females is analogous to the bulbourethral gland in males?
45. what gland on females is analogous to the prostate gland in males?
46. describe the blood supply for erectile tissue.
47. describe the nervous system's role in producing an erection.
48. what is detumescence and how does it occur?
embryology...
49. urogenital ridge is formed from...
50. germ cells arise from... and migrate to...
51. in male genital development, seminiferous tubules are formed from...
52. mesonephric duct becomes...
53. some mesonephric ducts become...
54. in female genital development, follicles are formed from...
55. describe oogonia development.
56. paramesonephric duct is formed by which hormones?
57. what does the cranial end of the paramesonephric duct grow into?
58. what does the caudal end grow into?
59. where does the sinovaginal bulb form?
60. what does the vagina form from?
61. what is uterine duplication caused by?
62. what are the characteristics of female pseudohermaphrotidism?
63. what does the genital tubercle develop into in males and females?
64. what does the urethral fold develop into in males and females?
65. what does the labioscrota develop into in males and females?
66. what is hypospadias?
67. testes descend through...
68. piece of peritoneum is retained as...
69. what is chryptorchism?
70. what is a congenital inguinal hernia?
71. what is a hydrocele?
answers
1. pelvic brim
2. levator ani+coccygeus, pudendal nerve, muscle suspended across lesser pelvis
3. body, isthmus, cervix, fundus
4. anteversion is the tilting of the uterus forward onto the bladder. anteflexion is the further bending of the uterus forward. (retroversion and retroflexion are the opposite)
5. round, transverse cervical, and uterosacral ligaments.
6. isthmus, ampula, infundibulum, ovary.
7. suspensory ligaments, ovarian ligaments
8. the parietal layer of the peritoneum that covers the reproductive organs.
9. the spaces in the vagina around the cervix.
10. the inner covering of the testis
11. testosterone
12. spermatogenesis
13. spermatogonia->spermatocytes->spermatids->mature sperm cells
14. leave the seminiferous tubule via the rete testis, which then dumps into the efferent ductules, which then converges into the epididymus, then to the ductus deferens.
15. a highly coiled tube that is 4-6 meters long, the site for sperm maturation.
16. inguinal canal
17. secretes viscous whitish-yellow fluid containing fructose
18. urethral crest of prostate.
19. prostatic ducts
20. embedded in the external urethral sphincter, lubricates penile urethra and neutralizes acid from urine. the last contributor to seminal fluid.
21. bulbourethral, seminal vescicle, prostate secretions.
22. main, submucosal, mucosal.
23. peripheral, central, transitional, periurethral. (from largest to most focused)
24. central and transitional.
25. peripheral zone.
26. prostatic acid phosphatase (PAP), fibrinolysin, citric acid, and prostate-specific antigen.
26b. increased PAP and PSA levels.
27. in the external oblique
28. in the transversalis fascia
29. transverus and internal oblique muscles
30a. through the inguinal canal and into scrotum
30b. the round ligament of the uterus, passes through inguinal canal to labia majora.
31. the venae comitantes that maintain thermoregulation in the spermatic cord.
32. the muscle innervated by genitofemoral nerve that raises the testes for thermoregulation.
33. protrusion of intestine through abdominal wall
34. direct is via a weakened conjoint tendon, indirect is through the inguinal canal.
35. clitoris
36. corpus cavernosum
37. labia minora
38. bulb of vestibule and glans clitoris
39. the tunica albuginea
40. separated by the vagina in females but surrounds the urethra in males. has less CT, therefore less turgidity.
41. overlies corpus cavernosus
42. overlies bulb of penis/vestibule
43. tauten perineal membrane
44. greater vestibular
45. urethral and paraurethral
46. internal iliac artery to internal pudendal artery to deep artery of the penis/clitoris
47. during erection, parasympathetic nerves (S2,3,4) dilate helicine arteries and allow blood to flow into erectile tissue
48. sympathetic nervous activity constricts helicine arteries and reroutes blood into venous plexus and deep dorsal vein.
49. intermediate mesoderm
50. yolk sac and gonad
51. sex cords
52. ductus deferens, seminal vesicles, ejaculatory duct.
53. efferent ductules
54. sex cords which form cortical cords, which form follicles.
55. oogonia form from germ cells, and undergo mitosis during fetal development. after birth no more oogonia are formed.
56. maternal or placental estrogens.
57. uterine tubes, ending in infundibulum that opens up into peritoneum.
58. uterus and vagina
59. where the paramesonephric ducts fuse with the urogenital sinus
60. the fusion of the bulbs, which begin to hollow out.
61. improper fusion or development of paramesonephric ducts.
62. masculinization of female external genitalia: partial fusion of labia majora, clitoral hypertrophy, and persistent urogenital sinus.
63. penis and clitoris
64. penile urethra and labia minora
65. scrotum and labia majora.
66. urethral openings on the ventral surface of the penis rather than at the glans.
67. inguinal canal, along gubernaculum.
68. tunica vaginalis
69. abnormal androgen production produces undescended testes.
70. patency of inguinal canal which allows intestines to enter scrotum
71. excess fluid in the tunica vaginalis.
the male reproductive anatomy basically follows spermatogenesis as it begins in the testes and ends at the penis. spermatogenesis occurs in the seminiferous tubules of the testis, aided by sertoli cells and leydig cells (which secrete testosterone). the spermatogonia in the walls of the tubules develop into spermatocytes, into spermatids, into spermatozoans, which are then released from the tubules. they travel into the rete testis, and into the ductus epididymus, which is a 4-5m long highly coiled tube where spermatozoans mature. from there they travel up the ductus deferens, which goes through the inguinal canal and behind the bladder, encountering the first of the ducts which combine with sperm to create seminal fluid.
the first of these is the seminal vesicles, which secrete a whitish viscous fluid containing fructose (recall the polyol pathway from biochemistry, and how sperm cells use fructose instead of glucose for metabolism). next is the ejaculatory ducts, which meet the urethra at the urethric crest of the prostate. next is the prostatic ducts in the prostate. finally, the bulbourethral gland is embedded in the external urethral sphincter and lubricates the penile urethra as well as neutralizing acidity from the urine.
some homologies of external genitalia between males and females are discussed: the penis and clitoris are both formed from the "genital tubercle". the "labiascrotal swelling" forms the scrotum in males and the labia majora in females. the urethral folds forms the urethra in males and the labia minora in females.
next we discuss the embryology of the reproductive systems. male/female differentiation begins around 4 weeks during development. before this point, germ cells in both sexes migrate from the yolk sac to the sex cords, forming the precursor to the gonads. in males, the mesonephric ducts (wolffian) develop while the paramesonephric (mullerian) ultimately degrade. the mesonephric ducts form the efferent ductules, ductus deferens, seminiferous tubules, and ejaculatory ducts.
in females, the follicles (recall the anatomy from the histology lecture) are formed by sex cords which form cortical cords, which form follicles. inside the follicles are oogonia, which began forming and dividing from the germ cells that migrated from the yolk sac. as mentioned above, the mesonephric duct eventually disappears and the paramesonephric duct develops into the female reproductive anatomy: the top of the ducts form the uterine tubes, ending in the infundibulum, and the bottom of the ducts form the uterus and vagina. the sinovaginal bulb is formed by the fusion of the urogenital sinus and the paramesonephric ducts, and the opening to the vagina forms by the hollowing out of the sinovaginal bulb.
some pathologies in development: hypospadias is the opening of the urethra in the ventral side of the penis instead of at the glans. chryptorchism is incomplete descent of the testis due to abnormal androgen production. congenital inguinal hernia is when the intestines come through the inguinal canal into the scrotal area. hydrocele is the acculumulation of fluid in the tunica vaginalis, which covers the testis.
questions
anatomy...
1. greater and lesser pelvis separated by...
2. what is the pelvic diaphragm made of?
3. what are the four parts of the uterus?
4. what are anteversion and anteflexion?
5. what is the connective tissue that holds the uterus?
6. what are the sections of the uterine tube?
7. what is the ovary held in place by?
8. what is the broad ligament formed from?
9. what are the fornices?
10. what is the tunica albuginea?
11. leydig cells secrete...
12. sertoli cells support...
13. describe spermatogenesis. (not on test)
14. describe the pathway of the sperm out from the seminiferous tubules to the ductus deferens.
15. describe the epididymus.
16. ductus deferens transports sperm cells through...
17. what do the seminal vescicles do?
18. where do the ejaculatory ducts open into the urethra?
19. prostate gland secrete into urethra via...
20. where is the bulbourethral gland? what does it do (2)?
21. what forms the seminal fluid?
22. what are the layers to the prostate?
23. what are the zones of the prostate?
24. what zones does hypertrophy of the prostate affect?
25. what zones does prostate cancer affect?
26. what does the prostate gland secrete? (4)
26b. what is an indicator for prostate cancer?
27. where is the superficial inguinal ring?
28. where is the deep inguinal ring?
29. conjoint tendon is the lowest part of...
30a. describe the path of the spermatic cord.
30b. what is the equivalent of the spermatic cord in the female and where does it pass through?
31. what is the pampiniform plexus?
32. what is the cremaster muscle?
33. what is an inguinal hernia?
34. what is the difference between a direct and indirect inguinal hernia?
what is the analogous erectile tissue on the female:
35. penis
36. corpus cavernosum
37. corpus spongiosum
38. bulb of penis and glans penis
39. what is it that imparts turgidity during an erection?
40. describe the corpus spongiosum.
41. describe the general purpose of the ischiocavernous muscle in males and females.
42. describe the general purpose of the bulbospongiosus muscle in males and females.
43. describe the general purpose of the transverse perinei muscle in males and females.
44. what gland on females is analogous to the bulbourethral gland in males?
45. what gland on females is analogous to the prostate gland in males?
46. describe the blood supply for erectile tissue.
47. describe the nervous system's role in producing an erection.
48. what is detumescence and how does it occur?
embryology...
49. urogenital ridge is formed from...
50. germ cells arise from... and migrate to...
51. in male genital development, seminiferous tubules are formed from...
52. mesonephric duct becomes...
53. some mesonephric ducts become...
54. in female genital development, follicles are formed from...
55. describe oogonia development.
56. paramesonephric duct is formed by which hormones?
57. what does the cranial end of the paramesonephric duct grow into?
58. what does the caudal end grow into?
59. where does the sinovaginal bulb form?
60. what does the vagina form from?
61. what is uterine duplication caused by?
62. what are the characteristics of female pseudohermaphrotidism?
63. what does the genital tubercle develop into in males and females?
64. what does the urethral fold develop into in males and females?
65. what does the labioscrota develop into in males and females?
66. what is hypospadias?
67. testes descend through...
68. piece of peritoneum is retained as...
69. what is chryptorchism?
70. what is a congenital inguinal hernia?
71. what is a hydrocele?
answers
1. pelvic brim
2. levator ani+coccygeus, pudendal nerve, muscle suspended across lesser pelvis
3. body, isthmus, cervix, fundus
4. anteversion is the tilting of the uterus forward onto the bladder. anteflexion is the further bending of the uterus forward. (retroversion and retroflexion are the opposite)
5. round, transverse cervical, and uterosacral ligaments.
6. isthmus, ampula, infundibulum, ovary.
7. suspensory ligaments, ovarian ligaments
8. the parietal layer of the peritoneum that covers the reproductive organs.
9. the spaces in the vagina around the cervix.
10. the inner covering of the testis
11. testosterone
12. spermatogenesis
13. spermatogonia->spermatocytes->spermatids->mature sperm cells
14. leave the seminiferous tubule via the rete testis, which then dumps into the efferent ductules, which then converges into the epididymus, then to the ductus deferens.
15. a highly coiled tube that is 4-6 meters long, the site for sperm maturation.
16. inguinal canal
17. secretes viscous whitish-yellow fluid containing fructose
18. urethral crest of prostate.
19. prostatic ducts
20. embedded in the external urethral sphincter, lubricates penile urethra and neutralizes acid from urine. the last contributor to seminal fluid.
21. bulbourethral, seminal vescicle, prostate secretions.
22. main, submucosal, mucosal.
23. peripheral, central, transitional, periurethral. (from largest to most focused)
24. central and transitional.
25. peripheral zone.
26. prostatic acid phosphatase (PAP), fibrinolysin, citric acid, and prostate-specific antigen.
26b. increased PAP and PSA levels.
27. in the external oblique
28. in the transversalis fascia
29. transverus and internal oblique muscles
30a. through the inguinal canal and into scrotum
30b. the round ligament of the uterus, passes through inguinal canal to labia majora.
31. the venae comitantes that maintain thermoregulation in the spermatic cord.
32. the muscle innervated by genitofemoral nerve that raises the testes for thermoregulation.
33. protrusion of intestine through abdominal wall
34. direct is via a weakened conjoint tendon, indirect is through the inguinal canal.
35. clitoris
36. corpus cavernosum
37. labia minora
38. bulb of vestibule and glans clitoris
39. the tunica albuginea
40. separated by the vagina in females but surrounds the urethra in males. has less CT, therefore less turgidity.
41. overlies corpus cavernosus
42. overlies bulb of penis/vestibule
43. tauten perineal membrane
44. greater vestibular
45. urethral and paraurethral
46. internal iliac artery to internal pudendal artery to deep artery of the penis/clitoris
47. during erection, parasympathetic nerves (S2,3,4) dilate helicine arteries and allow blood to flow into erectile tissue
48. sympathetic nervous activity constricts helicine arteries and reroutes blood into venous plexus and deep dorsal vein.
49. intermediate mesoderm
50. yolk sac and gonad
51. sex cords
52. ductus deferens, seminal vesicles, ejaculatory duct.
53. efferent ductules
54. sex cords which form cortical cords, which form follicles.
55. oogonia form from germ cells, and undergo mitosis during fetal development. after birth no more oogonia are formed.
56. maternal or placental estrogens.
57. uterine tubes, ending in infundibulum that opens up into peritoneum.
58. uterus and vagina
59. where the paramesonephric ducts fuse with the urogenital sinus
60. the fusion of the bulbs, which begin to hollow out.
61. improper fusion or development of paramesonephric ducts.
62. masculinization of female external genitalia: partial fusion of labia majora, clitoral hypertrophy, and persistent urogenital sinus.
63. penis and clitoris
64. penile urethra and labia minora
65. scrotum and labia majora.
66. urethral openings on the ventral surface of the penis rather than at the glans.
67. inguinal canal, along gubernaculum.
68. tunica vaginalis
69. abnormal androgen production produces undescended testes.
70. patency of inguinal canal which allows intestines to enter scrotum
71. excess fluid in the tunica vaginalis.
Wednesday, February 4, 2009
organ systems: embryology of the urinary systems
[picture courtesy of erika yosefah william shortbread zelfand]
this lecture is the last in the series of the kidney and looks at renal embryology. kidney development can be roughly divided into three phases: pronephros, mesonephros, and metanephros. pronephros is both the early evolutionary form of the renal filtering system and also the first stage in human kidney development. mesonephros has nephrons with glomeruli and s-shaped tubules, which filter blood from the aorta and drain it into the gut tube via the mesonephric duct. the formation of the last stage, metanephros, begins with signalling factors from the metanephrogenic mesenchyme that stimulate the growth of the "uretic bud" from the lower part of the mesonephric duct. the uretic bud branches out and anastomoses to form the renal tubules and framework for the kidney. one additional note regarding early development: the urorectal septum divides the gut tube into the anorectal canal and the urogenital sinus, which form the urinary and GI tracts.
some pathologies of kidney development: if kidney fails to "ascend" (a misnomer because the kidney stays in place while the body grows downwards) to its position deep to the 12th rib, this is called pelvic kidney. horseshoe kidney is the fusion of the kidneys below the inferior mesenteric artery, and a failure to ascend. duplications of a kidney / supernumerary kidney can occur if the uretic bud divides prior to the development of the metanephric mesoderm. agenesis is the lack of development of uretic bud, leading to inadequate contact between mesoderm and uretic bud, leading to lack of a kidney.
questions
1. urogenital and reproductive systems develop from..
2. early nephrons develop in...
3. what are the three stage is kidney development?
4. what are the characteristics of the mesonephros stage?
5. urine formation begins...
6. describe the excretion of metabolic waste in the embryo.
7. uretic bud branches out from...
8. what are the renal tubules formed by?
9. metanephrogenic mesenchyme initiates growth of uretic bud via...
10. what are the collecting ducts formed by?
11. what is the "ascent of the kidney"?
12. what is the urorectal septum's role in renal development?
13. what is pelvic kidney?
14. what is horseshoe kidney?
15. what is duplications of the kidney?
16. what is agenesis of the kidney?
answers
1. urogenital ridges of intermediate mesoderm.
2. lateral part of urogenital ridge.
3. pronephros, mesonephros, metanephros
4. nephrons consisting of glomeruli and S-shaped tubules, which filter blood from the aorta, and a duct that drains into the gut tube.
5. ~9 weeks
6. metabolic wastes are dumped into the gut via the mesonephric duct, absorbed into blood and transported across placental wall for removal.
7. mesonephric duct
8. repeated dichotomous branching of the developing metanephron.
9. signalling factors
10. uretic bud
11. the apparent ascent due to the growth of the embryo caudal to the kidneys.
12. the urorectal septum divdes the gut tube into the GI tube and the urinary system.
13. no ascent of kidney
14. kidneys fuse below inferior mesenteric artery and do not ascend
15. double kidneys develop because ureteric bud divides prior to development of metanephric mesoderm
16. lack of development of uretic bud leading to inadequate contact between bud and mesoderm.
Tuesday, December 9, 2008
ms anatomy: embryology of limbs
this lecture covered some basic ideas about the formation of limbs in an embryo. it covered: the structural development of limbs from somites, the formation of bones, formation of blood vessels, and some structural abnormalities.
somites are described as "paraxial mesodermal segments" that ultimately differentiate into three parts: sclerotome, which forms the spine and ribs, dermatome, which forms the dermal layer of the skin, and myotome, which forms the muscles of the back and limbs. the limb "bud" starts growing off of the lateral plate mesoderm, with migrating somatic cells contributing to its development as well. it grows outward, developing along the proximal-distal axis via FGF, spearheaded by the apical ectodermal ridge. the "zone of polarization activation" is what develops patterns in the caudal-cranial axis (such as the different sizes and shapes of the 5 fingers) via Shh. these two mechanisms feed off of each other in a positive feedback loop, where Shh from the ZPA promotes the FGF in the AER and vice versa, through intermediates called formin, gremlin, and bone morphogenetic protein.
the process of endochondrial ossification is then described briefly: mesenchymal cells condense and form "pre-cartilaginous aggregates". cartilage producing cells (chondroblasts) secrete BMP to promote growth and Ihh to promote BMP, another positive feedback mechanism. chondroblasts then secrete hyaline cartilage, and become chondroblasts that reside in empty pools called lacunae. hydroxyapetite, an inorganic calcium phosphate crystal, is then secreted and eventually kills off the chondrocytes via apoptosis. osteoblasts then secrete bone matrix and bone is formed. bone remodeling occurs through the balance of osteoblast (bone forming cells, formed from mesenchymally derived osteoprogenitor cells) and osteoclast (bone destroying cells, derived from fused mononuclear hemopoetic progenitor cells) activity on opposite ends of a surface of bone.
some facts about blood vessel development: angioblasts form vascular plexuses which form the aorta and cardinal veins. central artery distributes blood to marginal sinus, which becomes the basilic and cephalic veins. central artery becomes brachial and interossei arteries.
finally, some abnormalities of limb development: amelia is absence of limbs. meromelia is absence of limb segments. phocomelia is absence of proximal limb segments but normal distal segments. polydactylyl is extra digits. syndactylyl is webbed digits.
questions
1. what are somites made from and what induces them?
2. somites divide into...
3. what does the sclerotome become?
4. what does the dermatome become?
5. what does the myotome become?
6. describe the production of cartilage producing cells.
7. what do Wnt genes do?
8. where do the limb buds originate?
9. limb develops from both...
10. what is skeletal muscle formed from?
11. what is dermis formed from?
12. what is the epidermis formed from?
13. what are sensory neurons formed from?
14. what is the AER and what does it do?
15. what is the ZPA and what does it do?
16. what does the myotome form in the limbs?
17. describe the interaction between the AER and ZPA.
18. what are the signaling factors between the AER and ZPA?
19. describe the process of endochondral ossification.
20. what do cartilaginous cells secrete?
21. what is mineralization triggered by?
22. what are osteoblasts derived from?
23. epiphyseal plates expand...
24. achondroplasia is...
25. bone remodeled by...
26. osteoblasts are derived from...
27. osteoclasts are derived from...
28. osteoclasts are activated by...
29. amelia...
30. meromelia...
31. phocomelia...
32. polydactyly...
33. syndactyly...
34. angioblasts form...
35. central artery distributes...
36. marginal sinus becomes...
37. central artery becomes...
answers
1. made from paraxial mesoderm segments, induced by hox genes.
2. sclerotome, dermatome, myotome.
3. vertebrae and ribs
4. dermis
5. muscles of back and limbs
6. Shh from notochord and neural tube induce Pax (1,9) genes, which converted somitic cells into chondroblasts.
7. influence the conversion of dorsal somitic cells into dermatome and myotome.
8. lateral plate mesoderm.
9. local limb bud tissue, as well as migrating tissue from somites.
10. migrating mesoderm cells from myotome differentiate into muscle (following tendons during migration)
11. dermatomal cells
12. ectoderm
13. neural crest cells.
14. apical ectodermal ridge, forms bones along the proximal-distal axis via FGF.
15. forms bones along the cranial-caudal axis via Shh.
16. dorsal-ventral compartment muscles via Wnt.
17. the two centers have a positive feedback system where FGF from the AER maintains Shh expression at the ZPA and Shh in turn activates FGF in AER.
18. formin, gremlin, bone morphogenetic protein (BMP)
19. mesenchymal cells in center of limb condense into "pre-cartilaginous aggregates". chondroblasts form hyaline cartilage matrix. chondroblasts enlarge and form lacunae. hydroxyapetite deposits on partitions between lacunae. cartilage cells die by apoptosis. capillaries vascularize calcified cartilage. osteoblasts deposit bone matrix which replaces cartilage.
20. BMP to promote growth and Ihh to promote production of BMP
21. local secretion of alkaline phosphatase.
22. mesenchymally derived osteoprogenitor cells.
23. with growth hormone
24. premature ossification of epiphyseal plates
25. selective deposition and resorption of bone from opposing surfaces, depending on relative activity of osteoblasts and osteoclasts.
26. osteoprogenitor cells
27. "fused mononuclear hemopoietic progenitor cells"
28. cytokine signaling.
29. absence of limbs
30. absence of limb segments
31. absence of proximal end of limb with normal distal end
32. extra digits
33. webbed digits
34. vascular plexus with aorta and cardinal veins
35. blood through capillaries into marginal sinus
36. cephalic and basilic veins
37. brachial and interosseus arteries
somites are described as "paraxial mesodermal segments" that ultimately differentiate into three parts: sclerotome, which forms the spine and ribs, dermatome, which forms the dermal layer of the skin, and myotome, which forms the muscles of the back and limbs. the limb "bud" starts growing off of the lateral plate mesoderm, with migrating somatic cells contributing to its development as well. it grows outward, developing along the proximal-distal axis via FGF, spearheaded by the apical ectodermal ridge. the "zone of polarization activation" is what develops patterns in the caudal-cranial axis (such as the different sizes and shapes of the 5 fingers) via Shh. these two mechanisms feed off of each other in a positive feedback loop, where Shh from the ZPA promotes the FGF in the AER and vice versa, through intermediates called formin, gremlin, and bone morphogenetic protein.
the process of endochondrial ossification is then described briefly: mesenchymal cells condense and form "pre-cartilaginous aggregates". cartilage producing cells (chondroblasts) secrete BMP to promote growth and Ihh to promote BMP, another positive feedback mechanism. chondroblasts then secrete hyaline cartilage, and become chondroblasts that reside in empty pools called lacunae. hydroxyapetite, an inorganic calcium phosphate crystal, is then secreted and eventually kills off the chondrocytes via apoptosis. osteoblasts then secrete bone matrix and bone is formed. bone remodeling occurs through the balance of osteoblast (bone forming cells, formed from mesenchymally derived osteoprogenitor cells) and osteoclast (bone destroying cells, derived from fused mononuclear hemopoetic progenitor cells) activity on opposite ends of a surface of bone.
some facts about blood vessel development: angioblasts form vascular plexuses which form the aorta and cardinal veins. central artery distributes blood to marginal sinus, which becomes the basilic and cephalic veins. central artery becomes brachial and interossei arteries.
finally, some abnormalities of limb development: amelia is absence of limbs. meromelia is absence of limb segments. phocomelia is absence of proximal limb segments but normal distal segments. polydactylyl is extra digits. syndactylyl is webbed digits.
questions
1. what are somites made from and what induces them?
2. somites divide into...
3. what does the sclerotome become?
4. what does the dermatome become?
5. what does the myotome become?
6. describe the production of cartilage producing cells.
7. what do Wnt genes do?
8. where do the limb buds originate?
9. limb develops from both...
10. what is skeletal muscle formed from?
11. what is dermis formed from?
12. what is the epidermis formed from?
13. what are sensory neurons formed from?
14. what is the AER and what does it do?
15. what is the ZPA and what does it do?
16. what does the myotome form in the limbs?
17. describe the interaction between the AER and ZPA.
18. what are the signaling factors between the AER and ZPA?
19. describe the process of endochondral ossification.
20. what do cartilaginous cells secrete?
21. what is mineralization triggered by?
22. what are osteoblasts derived from?
23. epiphyseal plates expand...
24. achondroplasia is...
25. bone remodeled by...
26. osteoblasts are derived from...
27. osteoclasts are derived from...
28. osteoclasts are activated by...
29. amelia...
30. meromelia...
31. phocomelia...
32. polydactyly...
33. syndactyly...
34. angioblasts form...
35. central artery distributes...
36. marginal sinus becomes...
37. central artery becomes...
answers
1. made from paraxial mesoderm segments, induced by hox genes.
2. sclerotome, dermatome, myotome.
3. vertebrae and ribs
4. dermis
5. muscles of back and limbs
6. Shh from notochord and neural tube induce Pax (1,9) genes, which converted somitic cells into chondroblasts.
7. influence the conversion of dorsal somitic cells into dermatome and myotome.
8. lateral plate mesoderm.
9. local limb bud tissue, as well as migrating tissue from somites.
10. migrating mesoderm cells from myotome differentiate into muscle (following tendons during migration)
11. dermatomal cells
12. ectoderm
13. neural crest cells.
14. apical ectodermal ridge, forms bones along the proximal-distal axis via FGF.
15. forms bones along the cranial-caudal axis via Shh.
16. dorsal-ventral compartment muscles via Wnt.
17. the two centers have a positive feedback system where FGF from the AER maintains Shh expression at the ZPA and Shh in turn activates FGF in AER.
18. formin, gremlin, bone morphogenetic protein (BMP)
19. mesenchymal cells in center of limb condense into "pre-cartilaginous aggregates". chondroblasts form hyaline cartilage matrix. chondroblasts enlarge and form lacunae. hydroxyapetite deposits on partitions between lacunae. cartilage cells die by apoptosis. capillaries vascularize calcified cartilage. osteoblasts deposit bone matrix which replaces cartilage.
20. BMP to promote growth and Ihh to promote production of BMP
21. local secretion of alkaline phosphatase.
22. mesenchymally derived osteoprogenitor cells.
23. with growth hormone
24. premature ossification of epiphyseal plates
25. selective deposition and resorption of bone from opposing surfaces, depending on relative activity of osteoblasts and osteoclasts.
26. osteoprogenitor cells
27. "fused mononuclear hemopoietic progenitor cells"
28. cytokine signaling.
29. absence of limbs
30. absence of limb segments
31. absence of proximal end of limb with normal distal end
32. extra digits
33. webbed digits
34. vascular plexus with aorta and cardinal veins
35. blood through capillaries into marginal sinus
36. cephalic and basilic veins
37. brachial and interosseus arteries
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