Embryology Flashcards

1
Q

what makes up the female reproductive system?

A
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2
Q

what makes up the male reproductive system?

A
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3
Q

what is shown here?

A

Blastocyst

Blastocyst – outer layer of cells that goes to form the placenta and membranes

Inner ball of cells that goes to form the embryo proper

The blastocyst is a structure formed in the early development of mammals. It possesses an inner cell mass (ICM) which subsequently forms the embryo. The outer layer of the blastocyst consists of cells collectively called the trophoblast

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4
Q

Ectoderm ___, Mesoderm in ______, endoderm ______

Amniotic cavity _______ and yolk sac _______

Neural tube = ______________

Paraxial mesoderm = _______

Intermediate mesoderm = _____________

Lateral mesoderm = ____________

A

top

middle

bottom

above

below

brain and spinal cord

somite’s

forms urogenital systems

forms the bodies cavities

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5
Q

Intermediate plate mesoderm forms the ________ system

A

urogenital

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6
Q

timeline of events:

Weeks 1 & 2 – ________ formed

Week 3 – ________ (splits into 3 germ layers), neurulation (neural tube forms), _______ formation (paraxial mesoderm)

Weeks 4 – 8 - __________ period

Week 9 onwards – _________ of organ systems

A

blastocyst

gastrulation

somite

organogenetic

maturation

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7
Q

But…..Reproductive system Organogenesis:

  • _________ beyond 8 weeks
  • Extends beyond _________ period
A

Extends

post-natal

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8
Q
  • Reproductive and urinary systems have close ___________ links
  • Urinary system forms _________ for reproductive (part) system
A

embryological

template

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9
Q

Urinary system development - recap:

  • 3 sets of kidneys develop
  • _________ – cervical region – vestigial
  • _________ – thoracolumbar region – briefly functional
  • ________ – pelvic region – functional
  • Each acts as template for subsequent stage
A

Pronephros

Mesonephros

Metanephros

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10
Q

Pronephros, Mesonephros and Metanephros develop from what?

A

intermediate plate mesoderm

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11
Q

pictures show the week 5 embryo:

The ___________ that goes to start developing the reproductive system

Mesonephric ducts drain into the ______

Mesonephros is no longer ________ as part of the urinary system so is refunctioned to form the ______

A

mesonephros

cloaca

function

gonads

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12
Q

At about _ weeks mesonephros forms a long ovoid structure in association with thoracic and upper lumbar vertebrae

_______ part of mesonephric ridge becomes thickened to form a ___________ ridge

_______ ridge forms the substance of the ______

A

6

Medial

genital/gonadal

Gonadal

gonads

(Anteromedial part of the mesonephros (in blue in bottom right) thickens to form genital ridge)

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13
Q

Need cells that can undergo meiosis so they need to be undifferentiated and you wont find them in these 3 germ layers so need to import them form the _____ ____

Germ cells migrate into Genital ridge = ________ _______

  • Week 6 - ____ cells migrate from yolk sac, via dorsal mesentery, and embed into primitive sex cords (formed from mesenchyme of genital ridges)
  • This structure is known as the _________ gonad (why?) – no difference between male and female at this stage
  • No migration of germ cells - no ________
A

yolk sac

Indifferent Gonad

Germ

indifferent

gonads

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14
Q

what is the Paramesonephric duct?

A

Epithelium of the mesonephros invaginates to form a tube

This tube becomes the para-mesonephric duct

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15
Q

Paramesonpheric duct:

Develops lateral to developing gonads and __________ duct

Funnel shaped cranial end opens into __________ cavity

Caudally, cross ventral to __________ ducts

This projects into dorsal wall of _________ sinus

A

mesonephric

peritoneal

mesonephric

urogenital

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16
Q

what are the 3 main strucutres which go on to form the reproductive sytem in males and females?

A
  1. Indifferent gonad (with primordial sex cells that have moved in from the yolk sac)
  2. Mesonephric duct (Wolffian duct)
  3. Paramesonephric duct (Mullerian duct)
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17
Q

in males:

  1. Gonad forms _______
  2. Mesonephric duct develops into _______________________________
  3. Paramesonephric duct ____________
  4. Urogenital sinus forms ______________________
A

testis

epididymis, vas deferens, seminal vesicle,

degenerates

bladder, urethra; and prostate

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18
Q

In females:

  1. Gonad forms the ______
  2. Mesonephric duct ____________
  3. Paramesonephric duct forms ______________________
  4. Urogenital sinus forms ______________________
A

ovary

degenerates

fallopian tube, uterus, cervix part of vagina

bladder and lower part of vagina

19
Q

How does the indifferent gonad know whether to develop into a testis or an ovary? (Only difference is chromosomes)

what is the proccess in men? fill in the blanks in the picture

A
20
Q

study this histology

A

Sertoli cells have much lighter nucleus

Leydig cells in-between seminiferous tubules

21
Q

what is the process of testis development?

A

sex cords, medulla and cortex

Wk 6 priWk 5 – primary mordial germ cells incorporated into primary sex cords

Wk 7 – TDF stimulates primary sex cords - extend into medulla - seminiferous cords - tubules

Seminiferous cords branch, ends anastomose - rete testis of medulla

Surface epithelium (mesothelium) lost when thick capsule forms (tunica albuginea of adult testis)

Mesenchyme between cords gives rise to Interstitial cells of Leydig

By week 8, Leydig cells produce testosterone and other hormones which stimulate masculine differentiation of mesonephric ducts and external genitalia

In males, paramesonephric duct degenerates

22
Q

Testis – post natal development

what photo of the testis is prepubertal and which is postpubertal?

A

At puberty the seminiferous tubules become canalised and the Leydig cells make more testosterone

Reproductive system development doesn’t fully complete until puberty

23
Q

Seminal vesicles - Outgrowth from caudal end of ___________ duct

Prostate - Outgrowth(s) from _______ (from urogenital sinus)

Male external genitalia formed under the influence of __________

A

mesonephric

urethra

testosterone

24
Q

__________ duct disappears in females, opposite to males

A

Mesonephric

25
Q

Development of the gonad:

Indifferent stage

In the presence of TDF (No SRY region on chromosome so no tests determining factor) = gonad develops into a ______

In its absence gonad develops into an ______ (by default)

A

testis

ovary

26
Q

In a female foetus (XX chromosome):

No ___ region

No ___

By default the ________ gonad develops into an _____

A

SRY

TDF

indifferent

ovary

27
Q

Development of the ovary:

Primary sex cords _________ (leaving the primordial germ cells)

By 10 weeks secondary sex cords develop from surface __________

__________ germ cells become incorporated into them

Primordial germ cells then bud off with single surrounding layer of cortical cord cells to form primordial ________ (from ~16 weeks)

Active _______ of these early primordial follicles to form additional follicles

By _th month all follicles have formed

Oocytes enter _______ and arrested in prophase 1st meiotic division

Some follicular atresia by birth

A

degenerate

epithelium

Primordial

follicles

mitosis

7

meiosis

28
Q

Postnatal ovarian development:

~2 million primordial follicles at birth

Many follicles become atretic before puberty

After puberty, ________ influences stimulate 12-15 follicles, per 28 day cycle, to develop

Only ___ follicle (normally) reaches maturity and ovulation (unsure how selection is made for one)

Continues until the _________

A

hormonal

one

menopause

29
Q

Ovary – post natal development

what is A, B and C?

A

Childs ovary has millions of follicle

30
Q

Where do the tubular components of the female reproductive system come from?

A

Absence of testosterone causes degeneration of mesonephros and mesonephric duct

Paramesonephric ducts develop to give rise to female genital tract

31
Q

Origin of female genital tract:

Cranial (open funnel) end of paramesonephric duct becomes associated with ______

Caudal end of paramesonephric duct (uterovaginal primordium) becomes ______ and _____________________

Inferior part of vagina from ________ _____

(Mesonephric duct degenerates)

A

ovary

uterus

superior part of vagina

urogenital sinus

32
Q

Descent of the gonads:

Gonads initially form in lumbar region, so positional changes occur as development takes place

what is the descent process of the testis?

A
  • Week 7 – Level of T10 (Diaphragm undescended)
  • Week 12 – Level of deep inguinal ring (remains until 7th month)
  • Enters scrotum just prior to birth (39 weeks)

Descent due to the gubernaculum – fibrous cord

Gubernaculum contracts near birth and pulls the testes down

33
Q

Descent of the gonads:

Gonads initially form in lumbar region, so positional changes occur as development takes place

what is the descent process of the ovaries?

A
  • Week 7 – Level of T10
  • Week 12 – Broad ligament
  • Round ligament drawn through inguinal canal to attach to labrum majorum
34
Q

In females:

Once in the pelvis the gubernaculum stop contracting and degenerates and forms a fibrous cord and its remanents form the _______ ligament and the rest of the gubernaculum forms the ______ ligament

Ovary doesn’t pass through inguinal canal so ______ so less prone to developing inguinal _______

A

ovarian

round

narrow

hernias

35
Q

The following aspects are linked to the descent of the gonads:

  1. Formation of the larger _______ _____ in males
  2. In the female – the presence of the ______ ligament and its passage through the _______ ____
A

inguinal canal

round

inguinal canal

36
Q

when do things go wrong?

A
  1. Undescended testis
  2. Remnants – eg: gartner’s cysts (embryologic remnants of the caudal end of the mesonephric (Wolffian) duct)
  3. Anomalies of the paramesonephric duct in female
37
Q

what is Cryptorchidism?

A

a condition in which one or both of the testes fail to descend from the abdomen into the scrotum

When testes don’t descent as they should and they are not in the scrotum at birth

By 8th month they should of entered into scrotum

Want to find it in one of its location along its path

38
Q

Parents notice absence of testes in scrotum (cryptorchidism): when?

A
  1. Undescended
  2. Ectopic
  3. Retractile testes
  4. Absent testes
39
Q

What are some complications of undescended testis?

A
  1. Infertility
  2. Malignant transformation (germ cell tumours)
  3. Testicular torsion
40
Q

what is the mangement of undescended testss?

A

Orchiopexy (a surgery to move an undescended (cryptorchid) testicle into the scrotum and permanently fix it there)

41
Q

Remnants of mesonephric duct - what problems may it cause?

A

May form cysts

These swelling or cysts can have an impact on fertility and the womb

42
Q
  1. Anomalies of the paramesonephric duct

Forms the fallopian tube, uterus and vagina in females

May not fuse completely or duplicate

Can get two vaginas

Can cause difficult pregnancy

A
43
Q

Summary:

Mesoderm = _________ gonad

Mesonephric duct

SRY region of Y chromosome = ______ development = mesonephric duct becomes _______ _________. Also Mullerian Inhibiting Substance = ___________ duct degenerates

No SRY = gonad becomes _____, paramesonephric duct becomes ______________________________

A

Indifferent

testis

vas/ductus deferens

paramesonephric

ovary

fallopian tube, uterus, cervix and vagina