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Reproduction - Lian > Reproduction 1 - Origin of the sexes > Flashcards

Reproduction 1 - Origin of the sexes Flashcards

0
Q

What are testes?

A

The testis (testicles) are the male gonads. They are paired, ovoid reproductive glands that produce spermatozoa and male hormones, primarily testosterone.

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1
Q

List the main reproductive hormones and where they are secreted from

A

Hypothalamus:
Gonadotrophin Releasing Hormone (GnRH)
Prolactin Releasing Hormone (PRH)
Prolactin Inhibiting Hormone (PIH)

Posterior Pituitary:
Oxytocin
Anterior Pituitary
Follicle Stimulating Hormone (FSH)
Luteinising Hormone (LH)
Prolactin

Testes: Testosterone, Inhibin, Mullerian Inhibiting Hormone (MIH)

Ovaries: Oestrogen, Progesterone, Inhibin

Placenta: Human Chorionic Gonadotrophin (hCG), Human Placental Lactogen (hPL), Oestrogen, Progesterone

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2
Q

What are sertoli cells?

A

Associated with Seminiferous Tubules

Spermatozoa development

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3
Q

What are leydig cells?

A

Cells in the interstitial tissue

Secrete testosterone

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4
Q

Describe the testes relationship with the tunica vaginalis

A
  • The testis are suspended in the scrotum by the spermatic cords.
    The surface of each testis is covered by the visceral layer of TUNICA VAGINALIS, except where the testis attach to the epididymis and spermatic cord.
  • The parietal layer of the tunica vaginalis is adjacent to the internal spermatic fascia, is more extensive than the visceral layer and extends superiorly for a short distance onto the distal part of the spermatic cord; small amount of fluid between the two layers
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5
Q

Name the tough, fibrous outer surface of the testes

A

tunica albuginea

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6
Q

What is the mediastinum of the testes?

A

Area where the tunica albuginea thickens into a ridge on its internal, posterior aspect

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7
Q

How do the seminiferous tubules develop?

A

From the mediastinun, fibrous septums extend inward between lobules of long and highly coiled seminiferous tubules

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8
Q

What is the rete testis? How are they joined to seminiferous tubules?

A

Network of canals in the mediastinum of the testis. The seminiferous tubules are joined by straight tubules.

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9
Q

Describe process of spermatogenesis

A

1) Before birth, the germ cells colonise the sex cords in the primordial gonad; then proliferate by mitosis to form SPERMATOGONIA stem cells.
2) These begin mitosis to maintain a population of SELF-REGENERATING STEM CELLS that remain available up to and beyond the age of 70
3) At puberty, the cords hollow out to form the SEMINIFEROUS TUBULES, where sperms are produced. Each testis has 250-750 tubules, which empty into the rete testis, and from there form the epididymis.
4) A1 SPERMATOGONIA emerge from the stem cells. This marks the beginning of spermatogenesis in that part of the tubule.
5) Further DIFFERENTIATION to produce either more type A (stem) cells (remain at basal lamina) or Type B cells, which are committed to differentiation to spermatozoa.
6) Each Type B Spermatogonium then undergoes a fixed number of mitotic divisions to produce a CLONE (typically 64) of PRIMARY SPERMATOCYTES all linked together by cytoplasm bridges.
7) MEIOSIS of primary spermatocytes –> 2 haploid secondary spermatocytes –> 4 spermatids
8) Remodelling of spermatids –> sperm

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10
Q

How many spermatids does each A1 spermatogonium yield?

A

256

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11
Q

How many days does spermatogenesis take? New groups of A1 spermatogonia arise every how many days?

A

70 and 16 days

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12
Q

Where do spermatozoa mature?

A

Epididymis

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13
Q

How is sperm ejaculated? Name the process and what it is dependent on.

A

During copulation, contractions of the vas deferens sweep sperm to be mixed with other components of semen from the seminal vesicles (60% volume) and prostate (20% volume) in a process known as emission, which is dependent on the sympathetic nervous system.

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14
Q

Describe the composition of ejaculate and where sperm travel to in the female

A

A typical ejaculate of 3.5ml contains about 350 million sperm. Fewer than 50 will reach the site of fertilisation, the ampulla of the uterine tube, in the female tract.

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15
Q

Distinguish the spermatogenic cycle and spermatogenic wave

A

Spermatogenic Cycle: The development of a A1 Spermatogonia through to 256 sperms. The amount of time it takes for reappearance of the same stage of the cycle within a given segment of the tube.

Spermatogenic Wave: Different parts of the tube begin the spermatogenic cycle at different times, in a ‘wave’, so the production of sperm is constant. The distance on the tube between parts that are in the same stage is the spermatogenic wave.

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16
Q

Describe the role of the rete testis

A

A network of canals in the mediastinum of the testis that seminiferous tubules drain into.

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17
Q

What is the epididymis?

A

A convoluted duct, in which sperms are stored and continue to mature.

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18
Q

What is the role of the vas deferens?

A

A continuation of the epididymis, the vas deferens has relatively thick muscular walls and a minute lumen. During copulation these muscular walls contract, forcing sperm along the tube to be mixed with other components of ejaculate

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19
Q

Describe the role of the seminal vesicles

A

The seminal vesicles secrete a thick, alkaline fluid that is rich with fructose (energy source for sperms) and a coagulating agent. This fluid makes up ~60% of the volume of semen.
The duct of the seminal gland joins the ductus deferens to form the ejaculatory duct.

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20
Q

What is the prostate? What does it do?

A

A compound tubuloalveolar exocrine gland.

Prostatic fluid makes up ~20% of the volume of semen, and plays a role in activating sperms.

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21
Q

Describe the anatomy of the bulbourethral glands and what do they do?

A

The two pea-sized bulbourethral glands lie posterolateral to the intermediate part of the urethra, largely embedded within the external urethral sphincter.

The ducts of the bulbourethral glands open into the proximal part of the spongy urethra in the bulb of the penis.

Their mucus-like secretion enters the urethra during sexual arousal.

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22
Q

What are the ovaries?

A

The ovaries are almond shaped and sized female gonads in which oocytes develop. They are also endocrine glands that produce reproductive hormones.

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23
Q

How is the ovary suspended and connected to the uterus? What is the latter a remnant of?

A

Each ovary is suspended by a short peritoneal fold, or mesentery, the mesovarium. Medially within the mesovarium, a short ovarian ligament tethers the ovary to the uterus. The ovarian ligament is a remnant of the superior part of the ovarian gubernaculum.

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24
Q

Described the microstructure of the ovary

A

The connective tissue capsule of the ovary, the Tunica Albuginea of the Ovary, is covered with a smooth layer of ovarian mesothelium that has a dull, grayish appearance. This epithelium becomes progressively scarred and distorted because of the repeated rupture of ovarian follicles and discharge of oocytes during ovulation.

25
Q

What are the uterine tubes?

A

The uterine tubes (fallopian tubes) conduct the oocyte, discharged monthly from an ovary during child-bearing years, from the periovarian peritoneal cavity to the uterine cavity.

26
Q

What do primordial germ cells do in a female embryo?

A

Primordial germ cells colonise the cortex of the primordial gonad, becoming Oogonia.

27
Q

Describe how oogonia become primary oocytes

A

These proliferate rapidly by mitosis, so by 20 weeks of gestation there are over 7 million, however most of these die, leaving about 2 million that all begin meiosis before birth to become Primary Oocytes.

28
Q

What stimulates meiosis of oogonia? What do these cells form?

A

The Oogonia’s entry into meiosis 1 is stimulated by Mesonephric cells/aka Follicular cells - These are flattened epithelia cells, which surround the primary oocytes to form Primordial Follicles.

29
Q

Meiosis is then arrested at the diplotene stage (a resting stage) of prophase due to what? Where is thissecreted from?

A

Oocyte Maturation Inhibitor (OMI) secreted from the Follicular Cells.

30
Q

What are the 3 stages a female gamete must go through to mature.

A
  1. Pre-Antral or primordial follicle
  2. Antral, or secondary follicle
  3. Pre-ovulatory follicle
31
Q

What happens in the pre-antral or primordial follicle stage?

A

o The primary oocyte grows dramatically, but does not re-start meiosis
o Flat follicular cells become cuboidal Granulosa cells
o Granulosa cells secrete glycoprotein to surround the oocyte with a Zona Pellucida
o Surrounding connective tissue (stroma) cells form a Theca Folliculi
▪ Inner Theca Interna that is vascular and endocrine
▪ Outer Theca Externa that is a fibrous capsule
o Theca and Granulosa cells collaborate to secrete oestrogens

32
Q

What happens in the antral or secondary follicle stage?

A

o Granulosa cells continue to proliferate and a fluid appears between them, forming the antrum
o As more fluid forms, this secondary or Graafian follicle expands
o Expands to 2mm diameter without stimulation from reproductive hormones
o Continued development depends on reproductive hormones.
▪ FSH – Binds only to Granulosa cells
▪ LH – Binds only to Thecal cells

o Under the influence of LH, Thecal cells secrete androgens, which are converted to oestrogens by the Granulosa cells under the influence of FSH

33
Q

What happens in the pre-ovulatory follicle stage?

A
  • Phase begins 37 hours before ovulation; Oestrogen causes receptors for LH to appear on outer Granulosa cells
  • LH surge stimulates these receptors, leading to rapid changes in the follicle
  • Within 3 hours of the LH surge, the follicle restarts meiosis, and the first meiotic division is completed. This division is asymmetric; cytoplasm remains with one daughter cell and the other forms a condensed polar body.
  • The secondary follicle then enters meiosis II and arrests again 3 hours prior to ovulation.
  • Follicle size increases dramatically by increase in antral fluid volume to 25mm diameter
  • Structure begins to weaken
  • LH stimulates collagenase activity leading to follicle rupture
  • Ovum is carried out in the fluid and gathered up into the fallopian tube by fimbria
  • Meiosis is not completed unless the ovum is fertilised
    ▪ Unfertilised cells degenerate 24 hours after ovulation
34
Q

How is the corpus luteum formed? What does it do?

A

The theca cells surrounding the ruptured ovarian follicle are converted to corpus luteum - which secretes progesterone and oestrogen under the influence of LH.

In humans, the corpus luteum lives for 14 days before regressing spontaneously (in the absence of a fertilised ovum).

35
Q

Where is the round ligament of the uterus and what is its function?

A

The round ligament of the uterus originates at the uterine horns, in the parametrium. The round ligament leaves the pelvis via the deep inguinal ring,passes through the inguinal canal and continues on to the labia majora where its fibers spread and mix with the tissue of the mons pubis.
The function of the round ligament is maintenance of the anteflexion of the uterus during pregnancy

36
Q

List the female secondary sexual characteristics

A

Enlargement of breasts and erection of nipples.
Growth of body hair, most prominently underarm and pubic hair
Greater development of thigh muscles behind the femur, rather than in front of it
Widening of hips;lower waist to hip ratio than adult males
Changed distribution in weight and fat; more subcutaneous fat and fat deposits, mainly around the buttocks, thighs, and hips

37
Q

Name the principle secondary sexual characteristics in females

A

Enlargement of breasts and erection of nipples.
Growth of body hair, most prominently underarm and pubic hair
Greater development of thigh muscles behind the femur, rather than in front of it
Changed distribution in weight and fat; more subcutaneous fat and fat deposits, mainly around the buttocks, thighs, and hips

38
Q

Where from and how is oxytocin secreted?

A

Posterior pituitary - through neural control from the hypothalamus

39
Q

Where do germ cells arise from?

A

Epithelium of the yolk sac near the base of the developing allantois

40
Q

What are the primordial gonads developed from and where are they?

A

From somatic mesenchyme - Superficial and medial to the mesonephric tissue

41
Q

Sertoli cells express what gene?

A

SRY gene - only in males

42
Q

What ducts to male genitalia develop from?

A

Wolffian or Mesonephric ducts

43
Q

What ducts do female internal genitalia develop from?

A

Mullerian or para-mesonephric ducts

44
Q

What do sertoli cells secrete in the developing male?

A

Mullerian inhibiting hormone (MIH)

45
Q

What cells is testosterone secreted from in the developing male?

A

Interstitial cells

46
Q

What is the gubernaculum? What is its vestigial remnant?

A

Tethers testes to labioscrotal folds (future scrotum).

Scrotal ligament

47
Q

Labial scrotal swelling gives rise to what?

A

scrotum in men

labia majora in women

48
Q

What does the shaft of the penis and labia minora develop from?

A

Urethral folds

49
Q

What structures do the Müllerian ducts develop into

A

uterine tubes uterus
cervix
(upper vagina)

50
Q

What structures do Wolffian ducts develop into?

A

epididymis
vas deferens seminal vesicle

51
Q

Which hormones prevent the spontaneous development of the female genitalia in the male and from which cells are they secreted?

A

Interstitial cells of Leydig in the testes secrete androgens, principally testosterone, from 9 weeks gestation.

Sertoli cells lie within the walls of the seminiferous tubules and secrete MIH (Müllerian inhibitory hormone; MIS Müllerian inhibitory substance).

52
Q

What does the Urogenital sinus form in the male and female?

A

Male - prostate

Female - lower part of vagina

53
Q

What is the homologous structure to the male glans penis in the female

A

Clitoris

54
Q

Wolffian ducts depend on what hormone to develop?

A

Androgen - testosterone

55
Q

What causes urethral folds to fuse in male?

A

Androgens

56
Q

How long is the vas deferens in adult male?

A

45cm

57
Q

Each spermatogonium gives rise to what and how many?

A

64 primary spermatocytes

58
Q

One spermatocyte produces what?

A

4 spermatids

59
Q

How long are sperm stored in the epididymis and vas deferens respectively?

A

6-12 in epididymis, up to several weeks in vas deferens

60
Q

What is the tunica vaginalis a remnant of?

A

It is a peritoneal sac derived from the embryonic tunica vaginalis.

Reproduction - Lian (9 decks)

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