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ESA 4 > Reproduction > Flashcards

Reproduction Flashcards

1
Q

Define gonad

A

Protective structure in which gametes can be produced

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2
Q

What is the indifferent gonad derived from?

A

Intermediate mesoderm and primordial germ cells

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3
Q

Where do primordial germ cells originate and migrate?

A

Originate - yolk sac, migrate - retroperitoneum (along the dorsal mesentery)

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4
Q

Explain the embryological formation of testis

A

Male gametes have the Y chromosome (which has the SRY gene). Indifferent gonad therefore has medullary cord development (to form the definitive testis cordis), no cortical cords and a thick tunica albuginea

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5
Q

Explain the embryological development of the ovaries

A

Absence of a Y chromosome leads to the indifferent gonad having cortical cords with degeneration of medullary cords and no tunica albuginea

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6
Q

State how different cell types in the male embryo develop

A

Germ cells enter the definitive testis cordis (formed by medullary cords) and give rise to seminiferous tubules. Mesodermal cells give rise to Sertoli cells (which express SRY and MIS). Interstitial cells secrete testosterone.

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7
Q

State how different cell types in the female embryo develop

A

Germ cells are surrounded by mesenchymal cells which form primordial follicles. These oogonia are surrounded by a single layer of granulosa cells. No expression of the SRY gene

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8
Q

Describe the contents and function of internal male genitalia

A

Male internal genitalia consists of: duct system (epididymis, vas deferens and urethra), seminal vesicles, prostate gland and bulbo-urethral glands. Function - collect and mature sperm (continuous sperm production), production of other components of semen

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9
Q

Describe the contents and function of the external male genitalia

A

Consists of: penis, scrotum and testes. Function - delivers semen which is ejaculated during intercourse

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10
Q

Describe the contents and function of the internal female genitalia

A

Consists of: ovaries and duct system (fallopian tube, uterus, cervix and vagina). Function - provides an environment within which sperm can travel and fertilise the ova; conceptus can then implant, form a placenta and go on to develop into an embryo

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11
Q

Describe the contents and function of the external female genitalia

A

Consists of: vagina, vestibule, labia minora, labia majora and clitoris. Functions - provides a means for introducing sperm to the female reproductive tract. Also means the birth canal can be formed

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12
Q

Describe the development of the male external genitalia

A

The wolffian duct remains patent in males due to the presence of testosterone. Then goes on to produce the epididymis, vas deferens and seminal vesicles. Testis produces MIS which causes regression of the Mullerian duct

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13
Q

Describe the development of the female external genitalia

A

Wolffian duct regresses due to lack of testosterone. Mullerian ducts develop due to lack of MIS; the two Mullerian ducts fuse due to an inductive event where they touch the UGS. Eventually the septum regresses and the UGS grows (majority of vagina is formed by hindgut)

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14
Q

State what the three basic components of the indifferent gonad form in the male

A

Genital tubercule - glans penis
Genital folds - urethral folds and the shaft of the penis
Genital swellings - scrotum

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15
Q

State what the three basic components of the indifferent gonad form in the female

A

Genital tubercule - clitoris
Genital folds - labia minora and urethra
Genital swellings - labia majora

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16
Q

Describe the descent of the testis

A

Descends retroperitoneally. It arises in the upper lumbar regions and is tethered to the labioscrotal folds. Between 25 and 28 weeks the testis migrates over the pubic bone, behind the processus vaginalis. Above the testis the fascial layers become closely apposed. Evagination of the processus vaginalis occurs for the passage of the scrotum. Scrotal ligament is the vestigal remnant of the gubernaculum

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17
Q

Describe the movement of the ovaries in the embryo

A

Dont pass through the inguinal canal due to growth of uterus and uterine tube. Gubernaculum attaches the ovary inferiorly to the scrotal folds and becomes the ovarian ligament and round ligament of the uterus. Only thing in the inguinal canal in females is the round ligament of the uterus

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18
Q

Describe some common abnormalities of genital development

A

XY embryo with tissue that is unresponsive to testosterone can have female genitalia
XXY embryos have testes due to the presence of the Y
XO embryos might not have secondary female characteristics
PGC tumours can develop retroperitoneally
Hypospadias

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19
Q

List the main reproductive hormones and where they are produced

A

Hypothalamus - peptide releasing factors, GnRH, PRH and PIH
Posterior pituitary gland - oxytocin
Anterior pituitary gland - gonadotrophins (e.g. FSH/LH) and prolactin
Gonads - testosterone, oestrogens and inhibin
Placenta - hCG, hPL, oestrogens and progesterones

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20
Q

Describe the macroscopic structure of the testis

A

Ovoid reproductive organs that are suspended superiorly by the spermatic cord. Inferiorly the scrotal ligament holds them in place. Tunica vaginalis testis envelopes the testis in a double layer (except the superior and posterior borders where the spermatic cord and epididymis adhere to the testis)

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21
Q

Briefly describe the microscopic appearance of the testis

A

Composed of lobules of glandular tubules which are highly convoluted and held together by loose connective tissue with interspersed groups of interstitial tissue. Each tubule consists of: basement membrane (laminated connective tissue with numerous elastic fibres), flattened cells, external layer of flattened epitheloid cells and Sertoli cells.

22
Q

Describe the process of spermatogenesis

A

Spermatogonia divide into Ap and Ad spermatogonium. Primary spermatocytes divide by giving rise to secondary spermatocytes and then spermatids. Each primary spermatocytes forms 4 haploid spermatids

23
Q

Distinguish between the spermatogenic cycle and the spermatogenic wave

A

Cycle - time taken for reappearance of the same stage within a given segment of the tubule
Wave - distance between the same stage along the length of the tubule

24
Q

Describe spermiogenesis

A

When spermatids mature into motile spermatozoa. Spermiation occurs, removing any unnecessary cytoplasm and organelles. Spermatids are remodelled as they pass through the rete testis, ductuli efferentes and the epididymis

25
Q

When do sperm become motile?

A

When they reach the epididymis

26
Q

Describe the role of the rete testis

A

Removes fluid and concentrates the sperm. Carries sperm from the seminiferous tubules to the efferent ducts

27
Q

Describe the role of the epididymis

A

Stores sperm (for up to two days) and delivers it to the vas deferens. Walls are lined by pseudostratified epithelia (looks like two layers when there is only one). Head - stores sperm until it’s ready to undergo maturation. Body - maturation of sperm occurs here (takes about 1 week). Tail - connects to vas deferens; upon arousal contractions cause sperm to move into the vas deferens)

28
Q

Describe the role of the vas deferens

A

Transports mature sperm to the urethra in preparation for ejaculation

29
Q

Describe the role of seminal vesicles

A

Produce a sugar-rich fluid (fructose) that provides substrate for the sperm for energy production. Also produce amino acids, citrate and prostaglandins. Fluid from seminal vesicle makes up most of the ejaculatory fluid

30
Q

Describe the role of the prostate gland

A

Contributes additional fluid to the ejaculate which helps nourish the sperm. Secretes proteolytic enzymes and zinc. Urethra also runs through the prostate (potential pathological consequences)

31
Q

Describe the role of the bulbourethral glands in males

A

Located on the sides of the urethra. Produce a clear, slippery fluid that enters directly into the urethra - fluid lubricates and neutralises the urethra

32
Q

Describe sperm capacitation

A

Final step of sperm maturation. Occurs in the female genital tract because conditions there stimulate: removal of glycoproteins and cholesterol from the sperm membrane, activation of sperm signalling pathways and it allows sperm to bind to the zona pellucida of the oocyte and initiate the acrosome reaction

33
Q

Briefly describe the histological appearance of the ovaries

A

Outer cortex and inner medulla. Germinal layer made of cuboidal cells that coats the ovaries. Cortex - follicles and oocytes and is made of connective tissue that is tightly packed. Stroma of this CT is composed of fibroblasts. Medulla - ovarian vasculature and is composed of loose stromal tissue

34
Q

What is a follicle?

A

An oocyte surrounded by granulosa cells

35
Q

Describe the stages of follicular development

A

Primordial follicle - primary oocyte enters meiosis I and surrounded by follicular cells
Preantral - follicular cells become cuboidal and stratified (granulosa) with formation of zona pellucida
Antral - formation of antrum, several follicles develop
Preovulatory - one cell, one polar body with the cell entering metaphase II

36
Q

What is the corpus luteum?

A

Hormone secreting structure that appears after ovulation. Made when theca interna cells and granulosa cells become vascularised - develop a yellowish tint and change into lutein cells. Hormones it secretes are: oestrogen and progesterone

37
Q

Describe the hormones involved process of ovulation and their effects

A

FSH - triggers cumulus expansion in the preovulatory stage. Also trigger an increase in prostaglandins which then cause muscular contractions of the ovarian wall
LH - triggers signal transduction cascade which causes proteolytic enzymes (collagenase) to be secreted. These degrade the follicular tissue and form the stigma through which the ovum will leave

38
Q

Describe the mechanical features that stimulate ovulation

A

Fimbriae sweep over the surface of the ovary, uterine tube contracts rhythmically and the oocyte is carried into the tube by sweeping movements of fimbriae and cilia. Peristaltic muscular contractions of the tube then occur.

39
Q

If an oocyte is fertilised then explain what happens post-ovulation

A

Degeneration of corpus luteum is prevented by hCG production, therefore the corpus luteum continues to grow to become the corpus luteum of pregnancy (corpus luteum graviditatis). Cells continue to secrete progesterone until the fourth month, after which the placenta takes over

40
Q

Describe what occurs post-ovulation if fertilisation does not occur

A

The corpus luteum degenerates and becomes the corpus albicans. Progesterone production falls thus precipitating menstrual bleeding

41
Q

State some differences between spermatogenesis and oogenesis

A

Around 200M sperm/day vs 1 ovum every 28 days, 4 spermatids no polar bodies vs one ovum with two polar bodies, starts at puberty vs starts as a foetus, continues throughout adult life vs ends at menopause, motile gametes vs non-motile gametes, all stages complete in the testes vs last stage of meiosis II only occurs in the oviduct

42
Q

State the hormones involved in reproduction produced by the hypothalamus, anterior pituitary gland and gonads

A

Hypothalamus - GnRH
Anterior pituitary - FSH and LH
Gonads - progesterone, oestrogen, testosterone and inhibin

43
Q

List which cell types in the anterior pituitary gland produce which hormones

A 
Prolactin cells - prolactin
Somatotropic cells - growth hormone
Thyrotrophs - TSH
Corticotrophs - ACTH
Gonadotrophs - LH and FSH
44
Q

Describe the control of gonadotrophin secretion by the hypothalamus in males

A

Negative feedback by testosterone

45
Q

Describe the control of gonadotrophin secretion in females

A

Moderate titres of oestrogen reduce GnRH secretion whereas high titres promote GnRH secretion. Progesterone increases the inhibitory effects of moderate oestrogen and prevents positive feedback of high oestrogen. Oestrogen reduces GnRH per pulse whereas progesterone reduces the frequency of pulses

46
Q

Describe the effect of gonadotrophins on testes and ovaries

A

Trigger Gs subunit. Target cells - ovarian granulose cells, theca interna cells, testicular Sertoli cells and Leydig cells. Stimulate synthesis of sex hormones and control gamete production

47
Q

List the actions of LH and FSH in males

A

FSH - stimulates Sertoli cells to produce ABG and inhibin. ABG binds to testosterone and keeps it in the seminiferous tubules. Inhibin supports spermatogenesis and inhibits production of GnRH, LH and FSH
LH - stimulates Leydig cells in testicles to produce testosterone, promotes spermatogenesis and maintains the reproductive system

48
Q

Describe the effects of testosterone

A

Determinative - non-reversible and development of secondary sexual characteristics
Regulatory - maintenance of adult reproductive system

49
Q

List the actions of LH and FSH in females

A

LH - binds to thecal cells which secrete androgens which are converted by granulosa cells to oestrogen (under the influence of FSH)
FSH - stimulates production of inhibin which inhibits activin

50
Q

What are the three phases of menstruation?

A

Preparation of the gamete (ovarian cycle) and endometrium (uterine cycle)
Ovulation - release of the gamete
Waiting - pause in which the endometrium is maintained until a signal is received to indicate fertilisation has occurred

ESA 4 (3 decks)

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