Embryology Flashcards by Zachary Schulz

During what developmental week does urogenital development begin?

4th Week

How well did you know this?

Not at all

Perfectly

The urogenital ridge is made up of _______ and runs _________ from the cervical to lumbar region

Mesoderm

Posterolaterally

How well did you know this?

Not at all

Perfectly

The urogenital ridge forms along the _______ (ventral/dorsal) aspect of the _________ cavity

Dorsal

Ceolomic

How well did you know this?

Not at all

Perfectly

T/F: The urogential ridge is posterior to the vertebral region

False

It lies anterior to it

How well did you know this?

Not at all

Perfectly

What are the three regions of the urogenital ridge?

From top to bottom….

Pronephric Region

Mesonephric Region

Metanephric Region

How well did you know this?

Not at all

Perfectly

At 3 weeks gestation the pronephros forms in the _______ (cervical/lumbar) region of the embryo.

What does this function as until about 4 weeks gestation?

Cervical Region

It functions as the kidney

How well did you know this?

Not at all

Perfectly

After 4.5 week gestation the pronephros undergoes ________ and the ________ begins to take over.

Apoptosis

Mesonephros

How well did you know this?

Not at all

Perfectly

Which region does the mesonephros form?

During what gestational weeks does this preform filtration?

This is ultimately replaced by what?

Mesonephros forms in the upper thoracic and lumbar regions of the embyro

It performs filtration from gestational weeks 4-10

Ultimately replaced by metanephros

How well did you know this?

Not at all

Perfectly

T/F: Metanephros will become the adult kidney

True

How well did you know this?

Not at all

Perfectly

During what week of gestation does metanephros form?

What gestational week does it become functional?

Forms around gestational week 5

Becomes functional around gestational weeks 9-10

How well did you know this?

Not at all

Perfectly

During what gestational week do gonads begin to form?

Is the sex obvious at this point?

5-6th Week

The sex is not phenotypically obvious yet, this is referred to as the “indifferent” stage

How well did you know this?

Not at all

Perfectly

T/F: The mesonephric and paramesonephric ducts are destined to become gonads

True

How well did you know this?

Not at all

Perfectly

Gonads (testes & ovaries) develop from a thickening of the ventromedial surface of the urogenital ridge, called the ______ _____.

Gondal Ridge

How well did you know this?

Not at all

Perfectly

Which cells differentiate in the neck of the yolk sac around week 4 of gestation?

Primordial Germ Cells

How well did you know this?

Not at all

Perfectly

By the end of which gestational week do primordial germ cells become incorporated into the primary sex cords?

Gestational Week 6

How well did you know this?

Not at all

Perfectly

T/F: During the first 10 weeks of the “indifferent stage” only female genital ducts are present

False

Both male and female genital ducts are present

How well did you know this?

Not at all

Perfectly

From what two ‘ducts’ does the male duct system develop?

Mesonephric

Wolffian

How well did you know this?

Not at all

Perfectly

From what two ‘ducts’ does the female duct system develop?

Paramesonephric

Mullerian

How well did you know this?

Not at all

Perfectly

In males…..

What do the mesonephric ducts form?

During what gestational weeks does this occur?

Epididymis
Ductus Deferens
Efferent Ducts
Ejaculatory Duct

8-9th week of gestation (3rd Month)

How well did you know this?

Not at all

Perfectly

In females…..

What do the paramesonephric ducts form?

During what gestational weeks does this occur?

Fallopian Tubes
Uterus
Upper 1/3 - 2/3rds of the vagina

8-9th week of gestation (3rd Month)

How well did you know this?

Not at all

Perfectly

What unique protein does the SR-Y code for?

Testis Determining Factor (TDF)

How well did you know this?

Not at all

Perfectly

TDF causes _______ (Wolffian/Mullerian) ducts to differentiate into what?

Wolffian

Male Genital Structures, Gonads into Testis

How well did you know this?

Not at all

Perfectly

Once TDF differentiates gonads into testis, the testis release what?

What is the end result of this?

Mullerian Inhibiting Substance

This causes the mullerian Ducts to regress

How well did you know this?

Not at all

Perfectly

If there is no TDF present the ________ (Wolffian/Mullerian) ducts will regress.

Gonads will become what?

The Mullerian Ducts will become what?

Wolffian

Ovaries

Female Internal Genitalia

How well did you know this?

Not at all

Perfectly

What are the primary sex cords of the testes, which contain primordial germ cells?

Spermatic Cords (Testes Cords)

Spermatic Cords are well defined and lie within the ______ of the testes?

Medulla

Within the spermatic cord...... What do the epithelial cells become? What do the primordial germ cells become?

Epithelial Cells become sertoli cells ("nurse" cells from becoming sperm) PGCs become spermatoblasts

T/F: The spermatic cord remains solid until puberty

True

During puberty the spermatic cord canalizes to form what?

Seminiferous Tubules

The seminiferous tubules are seperated from one another by mesencyhme that gives rise to what? What are these responsible for making?

Interstitial Cells (Cells of Leydig) These cells make testosterone

What are TWO functions of fetal testes?

Produce Androgen which stimulates the development of Wolffian Ducts Produce Mullerian Inhibiting Substance which suppresses the formation of Mullerian Ducts

What if testes fail to ever develop in the fetus, or are removed from the fetus very early on?

Paramesonephric ducts will develop into female internal genitalia

What if ovaries fail to develop or are removed in the female fetus?

Has no effect on fetal sexual development– still female genitalia

In the presence of a structurally normal Y chromosome, which of the following structures would be expected to develop? A. Mullerian derivatives B. Ovaries C. Wolffian derivatives D. Uterus, cervix and upper 1/3 of the vagina

C. Wolffian Derivatives

A _____ is a common opening shared by the digestive, reproductive, and the urinary tracts

Cloaca

T/F: Humans develop a cloaca in utero

True

In what gestation week does the cloaca become divided in humans?

Gestational Week 7

During the indifferent stage..... A ______ tubercule developes at the ______ (anterior/posterior) end of the cloacal membrane. This will elongate to form what?

Genital Tubercle Anterior Elongates to form the phallus

T/F: By week 5 the cloaca has seperated into a urogenital and anal opening

False This occurs at week 7

The phallus elongates to form what? During this process the urogenital folds come together to form what structure?

The Penis The Urethra

Does the urethral opening typically form at the tip of the penis?

No, it gradually migrates to the tip of the penis

Fusion of what folds form the scrotum?

Labioscrotal folds

Incomplete fusion of the ureteral folds is referred to as what?

Hypospadias | this is typically more common distally

The testicles descend to the level of internal inguinal ring at about which time point during gestation?

7th Month

Which chromosome carries the genes for ovarian development?

X Chromosome

T/F: The ovary can be identified histologically prior to the 10th week of gestation

False The ovary can not be identified histologically until after the 10th week of gestation

In female development..... Around week 16 of gestation the primitive sex cords degenerate and are replaced by _____ ____ These eventually break up into isolated cell clusters which form ______ ____

Cortical Cords Primordial Follicles

What two types of 'cells' are contained in the primordial follicles?

Oogonium (form of PGC) Follicular Cells (surface epithelium, surround the oogonium)

T/F: Oogonia form postnatally

False All are formed prior to birth

How many oogonia remain at birth? At puberty?

Birth: About 2 Million Puberty: About 500,000

Which (two) genital ducts will become internal female genitalia?

Mullerian | Paramesonephric

In female embryos, the mesonephric ducts regress in the absence of what?

Testosterone

In female embryos, the paramesonephric ducts develop because there’s an absence of what?

Mullerian Inhibiting Substance

T/F: Female sexual development depends on the presence of ovaries or hormones

False It does not depend on the presence of hormones, just the absence of MIS

In female embryos..... The paramesonephric ducts move caudally into the future pelvic region. They will pass _______ (anteriorly/posteriorly) to the mesonephric ducts.

Anteriorly

The paramesonephric ducts fuse to form a Y-shaped _______ _______ in the midline. What will this structure ultimately become?

uterovaginal primordium this will ultimately become the uterus and upper vagina

In female development..... The fallopian tubes form from ____ (fused/unfused) cranial portions of the paramesonephric ducts

Unfused

The endometrial stroma (non-glandular part of the endometrium) and myometrium are derived from a special subset of mesodermal cells called ______ _______. In what TWO internal rgans is this mesoderm also found in?

Splanchnic Mesenchyme Heart Kidneys

In female development.... When the paramesonephric ducts fuse, the process also brings together two sides of a peritoneal fold that, when folded together, form what? This process also results in the formation of what TWO peritoneal compartments?

The Broad Ligament Rectouterine Pouch Vesicouterine Pouch

An enlargement at the end of the urogenital sinus induces the formation of paired endodermal outgrowths called what? This will eventually fuse to form what structure?

Sinovaginal bulbs These will eventually fuse to form the vaginal plate

In female development..... The urogenital sinus inverts and moves into the pelvic cavity to meet the sinovaginal bulbs....these two tissues fuse and canalize to form what structure?

The vagina

The _____ is formed by invagination of the posterior wall of the urogenital sinus

Hymen

in utero, where is estrogen produced? This places a role in what?

Placenta Fetal Ovaries This plays a role in feminization of the external female genitalia

T/F: The phallus will continue to grow in female development

False Phallus growth ceases and eventually becomes the clitoris

The urogenital folds fuse just behind (posterior to) the glans to form the _______ of the labia minora

Frenulum

The ______ (fused/unfused) parts of the urogenital fold form the labia minora

Unfused

The labioscrotal folds fuse posteriorly to form the posterior ______ _______.

labial commisure

Most parts of the labioscrotal folds remain unfused and form two large folds of skin called what?

Labia Majora

What are THREE of the steroid hormones invovled in the reproductive system? Which TWO of those are responsible for sexual growth characteristics?

Testosterone* Estrogen* Progesterone

All steroid hormones are derived from what?

Cholesterol

T/F: Progesterone is both an active steroid hormone and an important intermediary

True

The chemical conversion that happens in a particular organ/ tissue depends on the presence or absence of particular ______ in that organ/tissue.

Enzymes

If a person was missing the 21α-hydroxylase enzyme....... There would be an abundance of ______ There would be a shortage of ________

Abundance of testosterone Shortage of aldosterone

If a person was missing the 11 β-hydroxylase enzyme....... There would be an abundance of ______ and _______ There would be a shortage of ________

Abundance of testosterone and estrogen Shortage of aldosterone

Congenital Adrenal Hyperplasia (CAH) is due to a deficiency of what enzyme 90% of the time? In this disorder there is a deficiency of cortisol (sometimes aldosterone) which causes the fetal pituitary to make more of what? What is the end result of the above process?

21α-hydroxylase Causes the fetal pituitary to make more ACTH Eventually cortisol will be produced once enough precursor (ACTH) is made. However, the adrenals will enlarge due to the large amount of precursor. Testosterone amount is also drastically increased.

Do you expect to see changes in the external genitalia of males with CAH? Females?

Males: No Females: There would be an overly prominent clitoris, labia majora (This should prompt a work-up)

If you suspect CAH, you should check for urine or serum levels of what?

17-OHP

in females, where is estrogen produced?

Follicles of the ovaries

T/F: Estradiol is the most hormonally active form of estrogen?

True

What is the major form of estrogen produced by the ovaries?

Estradiol

Etriol is created in small amounts by the _____ and large amounts by the _______

Liver Placenta

Peripheral Hormone Conversions | occur in the presence of what?

Aromatase