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Anatomy #4- rumen, udder, urinary > Genitalia Development > Flashcards

Genitalia Development Flashcards

1
Q

Reproductive system germ layer derivatives

A

-Ectoderm: penis and clitoris

-Mesoderm: gonads (male or female), uterus, cervix, part of vagina, epididymis, ductus deferens, accessory sex glands
**main germ layer contributing to reproductive system

-Endoderm: most glands, portions of vagina and vestibule

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2
Q

Sex determination

A

-initially starts with fertilization by sperm (whether there is an Y chromosome or not)
-continues with gonad development and germ cell development

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3
Q

Gestation

A

Usually defined in 3rds but certain stages vary with different species
>development of male/female ducts can be in 1st or 2nd trimester
>testicular descent

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4
Q

Gamete progenitors

A

During formation of mesoderm and endoderm, a population of the epiblast cells are put aside to the definitive yolk sac and part of allantois for formation of germ line called primordial germ cells (PGCs). These totipotent cells can either form oocytes or sperm cells in future

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5
Q

Migration of primordial germ cells

A

They migrate due to chemotaxis through the stroma or into blood stream (depends on species), and back into urogenital ridge and gonadal ridge where they are incorporated into the intermediate mesoderm

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6
Q

Genital/gonadal ridge location

A

-genital ridge is right near the mesonephros (primitive kidney)

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7
Q

Gonadal ridge development

A

-also called bipotential gonad
-can differentiate along two paths: into an ovary or the testes

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8
Q

What happens when the primordial germ cells reach the gonadal/genital ridge?

A

They stimulate cells around them to proliferate causing ridge elongation

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9
Q

Origin of the gonadal/genital ridge cells

A

1.local mesenchymal cells (intermediate mesoderm)
2.Coelomic epithelium
3.Cells from mesonephric tubules

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10
Q

Primitive sex cord development

A

Develop from the cells of degenerating mesonephric tubules which form compact strands of tissue. The primitive sex cords will then incorporate the primordial germ cells

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11
Q

Sexually indifferent stage

A

-stage when the embryo is not committed to either sex

-stage where mesonephric ducts are present and will contribute to male reproductive system if gets correct signals

-stage also includes the paramesonephric ducts (near the mesonephric ducts) which will contribute to the female reproductive system if gets correct signals

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12
Q

Sex of an animal

A

Defined as its ability to produce a particular type of gamete (sperm or oocyte) along with the associated phenotypic traits (external genitalia)

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13
Q

What effects sex of animal?

A

-sex determining genes
-hormone encoding genes
-environment

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14
Q

Intersex individuals

A

-animals born with varying presentations of male and female genitalia

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15
Q

Genetic (genotypic) sex determination

A

-all mammals, birds, some other vertebrates, and some invertebrates

-sex initiation is determined by sex chromosome inherited at time of fertilization

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16
Q

Sex chromosomes in mammals

A

heterogametic: males XY

Homogametic: females XX

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17
Q

Environmental sex determination

A

-reptiles, lizards, many turtles, some fish, few snakes

-sex determination depends on external factors (eg. temperature)
-sex chromosomes are absent

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18
Q

What gene does the Y chromosome have?

A

-Sex determining Region on Y chromosome (SRY)
>produces the SRY protein (testis determining factor TDF)

19
Q

SRY protein effect

A

When SRY is produced by the primitive sex cords within the primitive gonad, the male reproductive system is stimulated

20
Q

Gonadal sex determination

A

-Whether the testes or ovaries develop or not

21
Q

Gonads (ovaries or testes) stimulating development

A

-gonads produce sex-specific hormones leading to development of internal genitalia (accessory sex glands, ducts) and Secondary sex characteristics as well as external genitalia

22
Q

Phenotypic sex

A

-determined after internal and external genitalia develop
-phenotypic sex is determined by the apparent anatomic sex of an individual

23
Q

Events leading to development of male reproductive system

A

1.Genotypic sex determination: SRY protein
2.Gonadal sex determination: testes develop
3.Phenotypic sex determination: development of penis, scrotum, and accessory sex glands

24
Q

Development of the testes

A

1.Undifferentiated sex cords begin to align themselves with rete tubules
2. ~5-15 mesonephric tubules will penetrate into primitive gonad but not connected with rete tubules. Paramesonephric duct serves no function here.
3. Rete tubules and mesonephric tubules become interconnected providing continuity between undifferentiated sex cords
4. Sex cords are now more epithelial in nature. Now called epithelial cords
5.Paramesonephric duct begins to degenerate under the direct influence of anti-mullerian hormone produced by cells that have formed in the developing testes
6. Primitive sex cords proliferate into seminiferous cords (solid tubules with germ cells) containing sertoli cells
7.At puberty, seminiferous cords become seminiferous tubules (continuity between rete testis and efferent ducts

25
Q

Seminiferous cords

A

-solid tubules
-peripheral layer of 15-20 mesonephric derived cells that will become sertoli cells which surround a central core of 4 pre-spematogonia

26
Q

Mesenchymal cells inbetween seminiferous cords

A

-develop into leydig or interstitial cells
-they also form connective tissue septa to divide the testis into a number of lobules that will contain the coords

27
Q

What does the mesonephric duct develop into?

A

develops into the epididymis and the ductus deferens

28
Q

Excurrent extragonadal duct system

A

-carries sperm through to the urethra
-includes the efferent ducts, epididymis and ductus deferens

29
Q

Accessory sex glands

A

-prostate
-bulbourethral glands
- seminal vesicles

**cats dont have seminal vesicles
**dogs only have prostate gland

30
Q

What develops from epithelial evaginations from mesonephric duct?

A

-vesicular glands
-ampullae ductus deferentis

31
Q

What develops from epithelial evaginations from urogenital sinus?

A

-prostate
-bulbourethral glands

32
Q

Testicular descent

A

-in most mammals, testes descend into scrotum

33
Q

General testicular descent

A

-Testis move a great distance from a position in body cavity to the scrotum. Requires rapid growth and then rapid regression of gubernaculum
-descent needs two layers of peritoneum covering the testis and descending with it (visceral vaginal trunk and parietal vaginal trunk)

34
Q

Two stages of testes descent

A
  1. Transabdominal phase
  2. Inguinal-scrotal phase
35
Q

Transabdominal phase

A

1.Testes are retroperitoneal, attached caudally to gubernaculum.
2. Gubernaculum will grow toward and into the scrotal region
3. Peritoneal cells form a junction with gubernaculum in inguinal region

36
Q

Inguinal-scrotal phase

A

1.When gubernaculum penetrates the inguinal ring with rapid growth (depends on androgens like tetosterone), the gubernaculum moves the testes into the inguinal canal.

  1. When testes are in the inguinal canal, they will enter the inguinal opening as the gubernaculum shrinks.

3.Shrinking pulls the testes deeper into the scrotum and each testis becomes surrounded by the inner layer of peritoneum called visceral vaginal tunic

4.inner visceral vaginal tunic cover the testis, epididymis and spermatic cord.
outer parietal vaginal tunic will be adjacent but not attached to inner tunic.

37
Q

Vaginal cavity

A

cavity between the inner visceral vaginal tunic and the outer parietal vaginal tunic
>allows each of the testis to move freely within the scrotum

38
Q

Cryptorchidism

A

-failure of one or both testes to descend into the scrotum
>unilateral:one testes retained
>bilateral:both testes retained

-testosterone is still produced in both cases, but spermatogenesis does not occur. Males still undergo typical male behaviour

39
Q

Where do the testes remain when cryptorchidism occurs?

A

-can be in abdomen or inguinal canal
-sometimes just under the skin in SQ tissues of groin

40
Q

Issues with lack of Testicular descent

A

-retained testes should be removed
-can develop into tumours
-appears to be heritable condition in animals

41
Q

Inguinal hernias

A

-vaginal cavity is continuous with peritoneal cavity which allows intestines to pass through this cavity and result in hernias

42
Q

What drives male external genitalia development?

A

-androgens, especially dihydrotestosterone

43
Q

External male genitalia development steps

A
  1. Androgens

2.genital tubercle elongates into phallus

3.urogenital folds form lateral boundaries of the urethral plate within which an epithelial cord known as urethral groove develops

4.urogenital folds fuse enclosing the urethral groove that now resembles a tube, called penile urethra

  1. urethral plate of tissue foes not extend to tip of penis. An ectodermal portion of tissue invaginates into the tip of the penis and will fuse with the endodermal cells lining the penile urethra. Forms tube/opening at tip
44
Q

Hypospadias

A

-urethra opens on the ventral surface of the penis rather than at the ends of the glans

-results from the failure of the urethral groove to close in the male.

-cause unknown but has been indicated as a potential inheritable defect in some dog breeds

Anatomy #4- rumen, udder, urinary (17 decks)

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