Fetal Embryology Flashcards by Lauren Lover

Urogenital anatomy begins to develop at what week developmentally?

~ wk 4

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Development of a ______ ______, occurs first in the fetus, which forms along dorsal aspect of _____ ____ (body cavity, lined w/ ______), Posterioolateral to the vertebral region.

Urogenital Ridge

coelomic cavity

mesoderm

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There are three regions of the urogenital ridge, the _____ region, a ____ region, and a ____ region

pronephric region

mesonephric region

metanephric region

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At 3 wks, a _______ forms in the cervical region of embryo, which functions [very minimally] as the ______.

It then differentiates into one ___ on each side

pronephros

kidney

long nephron

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By 4-4.5 wks, the embryo needs more filtration, and so the pronephros dies off by ______ as the _______ takes over, which forms in the _______ region and develops from (inferior/superior to inferior/superior).

apoptosis

mesonephros

upper thoracic-upper lumbar

Superior to inferior

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The mesonephros performs filtration from _____ wks gestation, with (all/not all) parts at once

~4-10 weeks

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At 4-5 wks, mesonephros filtration is replaced by the ______, which becomes the adult kidney, and part to all (depending on hormones present) of the mesonephric ducts are reabsorbed via ______.

metanephros

apoptosis

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The metanephros begins to form at wk ___ and becomes functional around wks ____

9-10

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Gonads begin to form during wks ____, which is considered the “_____ stage” because sex is not yet [genotypically/phenotypically] obvious.

5-6

indifferent; phenotypically

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______ and ______ ducts are destined to be gonads

mesonephric

paramesonephric

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Gonads (testes and ovaries) develop from a thickening of the ______ surface of the _______, called the gonadal ridge.

ventromedial

gonadal ridge

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When and where do primordial germ cells (PGCs) differentiate?

In the neck of the yolk sac early in the 4th week

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PGCs migrate to the _____ via a process called “____ ____”

genital ridge

amoeboid movement

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By end of ____ wk, the PGC become incorporated into the primary sex cords/gonads via diapedesis through the _______ (otherwise known as the _____ duct), which causes the ____ to grow

6th

umbilical cord

vitelline

gonads

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In developement of genital ducts __ weeks is the ____ stage

B/c Both male and female genital ducts are present

<10

Indifferent

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Male duct system develops from the _____

Mesonephric ducts form ___, ___, ___, ___

mesonephric/wolffian ducts

epididymis

ductus deferens

efferent ducts

ejaculatory duct

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Female duct system dev. from the ____

Paramesonephric ducts form ___, ____, ____

paramesonephric/mullerian duct

fallopian tubes

uterus

upper ⅔ of the vagina

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Development of the genital ducts Begins during the ___ month of gestation or __-__ wks

From here, much depends on the presence or absence of a __ chromosome, specifically, the presence of the ___ region of the this chromosome

3rd

8-9

sex-determining (SR-Y)

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SR-Y codes for a protein called ___

This protein causes ___ ducts to differentiate into male genital structures, the gonads to become testes, & testes make ____→ Mullerian (paramesonephric) ducts to regress

TDF (testis determining factor)

Wolffian (mesonephric)

Mullerian Inhibiting substance

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W/o an SR-Y region, there is no ___ → ___ ducts regress, gonads become ovaries, and there is no ____ → the Mullerian ducts develop into female internal genitalia

TDF

Wolffian

mullerian inhibiting substance

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____ are Primary sex cords of testes containing primordial germ cells.

They are well-defined cords w/in the ___ of the testis

testes cords (spermatic cords)

medulla (middle)

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The Testes cords (spermatic cords) contain two types of cells:

____, _____

Epithelial cells

Primordial germ cells

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Epithelial cells become_____

Primordial germ cells become____

Sertoli cells (nurse cells for developing sperm)

Spermatoblasts

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The spermatic cords remain ____ until puberty

They then ____ to form ____

solid

canalize

seminiferous tubules (ST)

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Seminiferous tubules are separated from each other by \_\_\_, giving rise to\_\_\_\_, which make \_\_\_\_

mesenchyme interstitial cells (cells of Leydig) testosterone

Fetal testes produce ___ whi Stimulate dev. of the \_\_\_\_, Suppress formation of the \_\_\_

androgens mesonephric (Wolffian) ducts paramesonephric (Mullerian) ducts

If the testes fail to develop in the fetus, or are removed from the fetus early on, ____ will develop into female internal genitalia If ovaries fail to develop or are removed in the female fetus, there (Is/Is no) effect on fetal sexual development

paramesonephric ducts IS NO

A __ is a common opening shared by the digestive/reproductive/urinary tracts Humans this develops in utero, but it becomes divided by __ of gestation

cloaca wk 7

Cloacal separation In the indifferent stage: \_\_\_ develops at anterior end of cloacal membrane, it slongates eo form the \_\_\_ \_\_\_\_ swellings and _____ folds appear

Genital tubercle phallus (gonad) Labioscrotal, Urogenital

In male external genitalia, the ___ elongates to form the penis Elongation pulls the urogenital folds together Folds fuse to enclose the urethra, urethral opening moves towards (end/bottom) of penis

Phallus Bottom

Labioscrotal swellings meet ___ and fuse, forming scrotum labioscrotal folds move inferior to the urogenital sinus and then fuse→ urogenital folds do the same Fusion of the urogenital folds creates the ___ and the \_\_\_\_

posteromedially penis, elongated urethra

\_\_\_\_ is Incomplete fusion of urethral folds→ typically more distal

Hypospadias

Descent of the testes occurs due to the pulll from the ____ & tethers the testes in the scrotum. Descent of the testes to the level of the internal inguinal ring occurs __ month gestation.

gubernaculum shortening ~ 7

Gonadal development occurs (Fast/Slow) in females Until \_\_\_\_, the ovary cannot be identified histologically

SLOW wk 10

\_\_\_ carry the genes for ovarian development \_\_\_ genes also appear to play a role in ovarian development

X chromosomes Autosomal

Early fetal period: Cords of ____ (sex cords) extend from surface epithelium of the developing gonad into the underlying mesenchyme (think surface area). The ___ comes from mesodermal tissue (pertains to ovarian development) Sex cords ↑ in size & ____ cells are incorporated into them \_\_\_ weeks: those cords begin to break up, forming \_\_\_\_

Cortical tissue Epithelium primordial germ ~16 primordial follicles

Primordial Follicles consists of ___ & \_\_\_\_

Oogonium: from a primordial germ cell Follicular Cells: from surface epithelium and surround oogonium as a layer of flattened cells

Active ___ of the oogonia occurs during fetal life, producing millions of primordial follicles ~20 wks (No/more) oogonia form postnatally→ all are formed prior to birth ~2 million remain to become primary oocytes at time of birth; by puberty ~ ____ remain

mitosis NO ½ million remain

In female embryos, the mesonephric ducts regress in the absence of \_\_\_ Female sexual development (does/does not) depend on the presence of ovaries or hormones→ just on the absence of MIS, which is coded for in the SR-Y region

testosterone Does not

Both of the paramesonephric ducts pass caudally and reach the future pelvic region They cross-over (anterior/posterior) to the mesonephric ducts to meet at the midline in the pelvic region and fuse to form a _____ in the midline This tubular structure projects into dorsal wall of urogenital sinus, will become the\_\_\_\_ and \_\_\_\_

Anterior Y-shaped uterovaginal primordium uterus & superior part of vagina

From where do the Fallopian tubes develop

develop from the unfused, cranial part of the paramesonephric ducts

Endometrial stroma (structural, non-glandular part of the endometrium) and myometrium are derived from a special subset of mesodermal cells called ____ (also found in heart & kidneys)

splanchnic mesenchyme

When paramesonephric ducts fuse, the process also brings together two sides of a peritoneal fold that, when folded together, form the \_\_\_. The process also forms two peritoneal compartments: ___ and \_\_\_\_

broad ligament Rectouterine pouch Vesicouterine pouch

Enlargement at end of uterovaginal primordium induces formation of paired endodermal outgrowths called \_\_\_, which fuse to form a ___ → later, central cells of vaginal plate break down, forming the \_\_\_\_

sinovaginal bulbs vaginal plate vaginal lumen

At the most caudal part of uterovaginal canal, the sinovaginal bulbs meet w/ urogenital sinus; the urogenital sinus inverts, and moves into the pelvic cavity to meet the sinovaginal bulbs→ the 2 sets of tissue fuse and canalize, forming the \_\_\_\_\_.

vagina

The ____ is formed by invagination of the posterior wall of urogenital sinus, resulting from expansion of caudal end of the vagina

Hymen

What hormone from placenta & fetal ovaries are involved in feminization of external genitalia?

Estrogen

In females the Phallus grows but remains small, becoming the \_\_\_

clitoris

Clitoris is relatively large at 18 wks→ it develops like a penis, but the urogenital folds only fuse just posterior to the glans to form the frenulum of the \_\_\_→ the unfused parts of the urogenital folds form the \_\_\_\_

labia minora labia minora

Labioscrotal folds fuse posteriorly to form the ____ and fuse anteriorly to form anterior\_\_\_ and \_\_\_\_

posterior labial commissure labial commissure and mons pubis

Most parts of the labioscrotal folds remain unfused and form 2 large folds of skin called ____ (homologous to the \_\_\_)

labia majora

Describe the structure of Steroids and how they are distinguished from each other , derived from cholesterol & closely related

4-ring structure of carbon atoms by their side chains

What are steroids derived from and where are they made?

cholesterol & closely related Ovaries Testes adrenal glands

What are the 3 steroid hormones

Testosterone Estrogen Progesterone

\_\_\_\_ is an active steroid hormone & an important intermediary

Progesterone

\_\_\_\_\_\_\_ is Cortisol deficiency (sometimes Aldosterone) occurs, causing fetal pituitary to make more ACTH, causing cortisol to be made but much more androgen is made as well

Congenital Adrenal Hyperplasia (CAH)

90%+ of the time, CAH is due to ______ deficiency in a developing fetus

21α-hydroxylase

In Congenital Adrenal Hyperplasia (CAH) what happens to the Adrenals how does this impact the hormones being produced? how does this impact the female and male genitalia

They enlarge because of the cortisol precursor they make Normally, the adrenal cortex makes a small amount of testosterone→ in this case, testosterone is drastically ↑ Females appear significantly different phenotypically, males will appear the same

What is the test for CAH

check their serum and urine for elevated 17-OHP (precursor to 21a-hydroxylase)

T/F Congenital Adrenal Hyperplasia (CAH) → is an EMERGENCY

True

The genital tubercle becomes the ____ in females and the ____ in males

F = clitoral glans M= glans penis

the Urogenital folds become the ____ in females and the ____ in males

F= vuval and labial openings M = Phallic shaft

the scrotum in men are homologu to the ___ in females

Labia majora

the fore skin on men is homologus to the ___ and ____ in females

labia minora clitoral hood

Estrogen controls dev.of ____ and promotes _____ development In females, estrogen is produced by the \_\_\_\_

2° sex characteristics normal bone developing follicles of the ovaries

Estrogen variants

Estradiol (E2) Estrone (E1) Estriol (E3)

\_\_\_\_\_Less-active form of estrogen; created in ↓lvls in fat cells when steroids are stored there

Estrone (E1):

\_\_\_\_ Much less active form→ created in small amounts in the liver; created in ↑ amounts in placenta; can be used as a marker for Neural Tube Defects

Estriol (E3):

\_\_\_\_ is a Major form of estrogen made by ovaries; most hormonally-active

Estradiol (E2):

Peripheral Hormone Conversions of estrogen occur in the presence of \_\_\_

Aromatase

Only\_\_\_, ___ steroid hormone can participate in enzymatic rxns

free, unbound

Estrogen target tissues include:

Brain (hypothalamic/pituitary) CV mammary gland liver reproductive tract (uterus/cervix/vagina/ovary/testes/prostate) bone

Fetal Embryology Flashcards

(72 cards)