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PHYSIOLOGY IV > LECTURE 7 (Male hormones) > Flashcards

LECTURE 7 (Male hormones) Flashcards

1
Q

Describe the anatomy of the male sexual organs

A

Testis is composed of 900 SEMINIFEROUS TUBULES where sperm are formed -> sperm empty into the EPIDIDYMIS which leads into the VAS DEFERENS which enlarges into the AMPULLA OF THE VANS DEFERENS before entering the body of the PROSTATE GLAND -> contents from the TWO SEMINAL VESICLES empty into an EJACULATORY DUCT into the INTERNAL URETHRA + PROSTATIC DUCTS contents empty into an EJACULATORY DUCT into the PROSTATIC URETHRA -> URETHRA is supplied with mucus from URETHRAL GLANDS (along its length) and BULBOURETHRAL GLANDS (COWPER GLANDS) near the origin of the urethra

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2
Q

How is sperm formed?

A

1) During the formation of the embryo, PRIMORDIAL GERM CELLS migrate into the testes and become SPERMATOGONIA (premature germ cells) lying in 2-3 layers of inner surfaces of seminiferous tubules
2) Spermatogonia begin to undergo mitotic division during puberty and continue to differentiate and proliferate into SPERM

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3
Q

How long does Spermatogenesis occur?

A

74 days

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4
Q

What are the steps of Spermatogenesis?

A

1) Spermatogonia migrate among Sertoli cells towards the central lumen of the seminiferous tubule
2) Spermatogonia enlarge to form PRIMARY SPERMATOCYTES that undergo meiotic division to form two SECONDARY SPERMATOCYTES
3) Spermatocytes divide to form SPERMATIDS that are modified to become SPERMATOZOA

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5
Q

Describe the anatomy of the sperm

A
  • Head composed of condensed nucleus of cell + thin cytoplasmic and cell membrane layer
  • Anterior 2/3 of head is ACROSOME has hyaluronidase and proteolytic enzymes (allows sperm to enter ovum + fertilise it)
  • Tail consists of axoneme (central skeleton of 11 microtubules), thin membrane covering the axoneme and mitochondria in the body of tail
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6
Q

What are the hormones that stimulate spermatogenesis?

A
  • Testosterone = secreted by Leydig cells + essential for growth and division of testicular germinal cells
  • LH = secreted by anterior pituitary gland + stimulates Leydig cells to secrete testosterone
  • FSH = secreted by anterior pituitary gland + stimulates Sertoli cells to convert spermatids to sperm
  • Oestrogens = formed from testosterone by Sertoli cells when stimulated by FSH + essential for spermiogenesis
  • Growth hormones = promote early division of spermatogonia
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7
Q

When do sperm become motile?

A

Sperm in the early portions of the epididymis are non-motile but become motile 18-24 hours being in the epididymis

ADDITIONAL INFO: several inhibitory proteins in the epididymal fluid prevent final motility until after ejaculation

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8
Q

Where is Sperm stored?

A

A small amount is stored in the epididymis but a large amount is stored in the vas deferens, for at least a month

ADDITIONAL INFO: After ejaculation, sperm become motile and can fertilise the ovum, a process called MATURATION

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9
Q

What increases the activity of sperm?

A
  • Neutral + slightly alkaline medium (e.g semen)
  • Increase temperature
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10
Q

What is the function of Seminal vesicles?

A

It secretes nutrient contents into the ejaculatory duct which provides the sperm of nutrients until it fertilises the ovum

Explanation: Seminal fluid contains fructose, citric acid, prostaglandins, fibrinogen and other nutrient substances

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11
Q

How do prostaglandins help aid fertilisation?

A
  • React with female cervical mucus to make it more receptive to sperm movement
  • Cause backward, reverse peristaltic contractions in the uterus + fallopian tubes to move ejaculated sperm towards the ovaries
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12
Q

What is the function of the prostate gland?

A
  • It secretes a thin, milky fluid containing calcium, citrate ion, phosphate ion, a clotting enzyme and profibrinolysin
  • Secretion is alkaline so can prevent sperm from dying in acidic conditions
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13
Q

How long can sperm last inside the female?

A

24-48 hours at body temperature

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14
Q

What happens during “Capacitation” of spermatozoa?

A
  • Uterine and Fallopian tube fluids wash away the various inhibitory factors that suppress sperm activity in the male genital tracts
  • Cholesterol in the seminiferous tubule cover the acrosome to toughen membrane + prevent release of enzymes -> after ejaculation, sperm swim away from cholesterol vesicle
  • Membrane becomes more permeable to Ca2+ -> more movement + acrosome enzymes released more rapidly
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15
Q

What are the functions of Hyaluronidase and Proteolytic enzymes?

A

Hyaluronidase = depolymerises hyaluronic acid polymers in the intercellular cement that holds the ovarian granulosa cells together

Proteolytic enzymes = digest proteins in structural elements of tissue cells that adhere to the ovum

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16
Q

What happens in the “Acrosome reaction”?

A

Sperm go through the granulosa cell layers + penetrate through the zona pellucida -> Anterior membrane of sperm binds to receptor proteins in zona pellucida + entire acrosome dissolves + acrosomal enzymes are released -> Sperm head + oocyte fuse to form a single cell

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17
Q

Why does only one sperm enter the oocyte?

A

A few minutes after the first sperm penetrates the zona pellucida of the ovum, Ca2+ diffuse inward through oocyte membrane causing CORTICAL GRANULES to be released by oocyte into the PERIVITELLINE SPACE -> granules contain substances that prevent binding of additional sperm + cause any sperm that have already begun to bind to fall off

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18
Q

What is the effect of temperature on Spermatogenesis?

A

Increasing the temperature of the testes can prevent spermatogenesis by causing degeneration of cells of seminiferous tubules including spermatogonia

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19
Q

What is Cryptorchidism?

A

Failure of a testis to descend from the abdomen into the scrotum at or near the time of birth of a foetus

SIGNIFICANCE:
A testis that remains in the abdominal cavity/inguinal canal is incapable of forming sperm + tubular epithelium becomes degenerate, leaving only the interstitial structures of the testis [caused by the increase of temp since testis is close to the body]

TREATMENT:
- Testosterone
- Surgery
BOTH used to descend testes

20
Q

Why is the “glans penis” the most important source of sensory nerve signals to initiate the male sexual act?

A

The slippery massaging action of intercourse on the “glans” stimulates the sensory end-organs -> signals pass through the pudendal nerve then through the sacral plexus -> then pass into the sacral portion of the spinal cord + up the undefined areas of the brain

ADDITIONAL INFO: surrounding areas can also stimulate sexual desire including inflammation + mild infection of sexual organs

21
Q

How does “Erection” happen?

A

1) Parasympathetic impulses pass from the sacral portion of the spinal cord through the pelvic nerves to the penis + release NO, VASOACTIVE INTESTINAL PEPTIDE & ACETYLCHOLINE
2) NO activates guanylyl cyclase -> increase formation of GMP -> GMP relaxes arteries of penis and meshwork of smooth muscle fibers in the erectile tissue of the CORPORA CAVERNOSA and CORPUS SPONGIOSUM
3) As vascular smooth muscles relax, blood flow into penis increases -> release of NO causing further vasodilation

22
Q

Is lubrication a parasympathetic function? (YES/NO)

A

YES

Explanation: Parasympathetic impulses cause urethral + bulbourethral glands to secrete mucous

23
Q

What are the steps of “Emission” and “Ejaculation”?

A

1) Sexual stimulus becomes extremely intense -> reflex centers of the spinal cord emit sympathetic impulses that leave the cord at T12 to L2 + pass to the genital organs through the hypogastric and pelvic sympathetic nerve plexuses to initiate EMISSION
2) Vas deferens + ampulla contract to expel sperm into the internal urethra -> contractions of prostate gland + seminal vesicles expel prostatic and seminal fluid into the urethra, forcing the sperm forward [EMISSION]
3) Sensory signals excite rhythmical contraction of internal genital organs + rhythmical, wavelike increases in pressure in both the erectile tissue of the penis and the genital ducts and urethra causes “EJACULATION”

24
Q

What is Resolution?

A

After ejaculation, male excitement disappears almost entirely within 1-2 mins and erection ceases

25
Q

Where is testosterone formed?

A

Interstitial cells of Leydig

ADDITIONAL INFO: almost non-existent during childhood when testes secrete almost no testosterone but are numerous during the first few months of life and after puberty

26
Q

Describe the metabolism of Testosterone

A
  • Either loosely bound with plasma albumin or more tightly bound with sex hormone-binding globulin
  • Circulates in blood for 30 mins to several hours
    [then is either transferred to tissues or degraded into inactive products]
  • Converted by tissues into dihydrotestosterone
27
Q

What is the function of Testosterone during foetal development?

A

The formation pf the prostate gland, seminal vesicles and male genital ducts while suppressing the formation of female genital organs

Explanation: SRY gene on the Y chromosome encodes a protein called the testis determining factor -> Initiation of cascade of gene activations that cause genital ridge cells to differentiate into cells that secrete testosterone and become testes -> formation of penis and scrotum

28
Q

What are the effects of testosterone on males?

A
  • Causes growth of hair
    [pubic hair, libia alba above abdomen, face, chest and back]
  • Decreases the growth of hair on top of the head
  • “cracking voice” [caused by hypertrophy of laryngeal mucosa and enlargement of the larynx]
  • Increases the thickness of skin + excessive secretion of sebaceous glands
    [can result in acne]
  • Increase protein formation and muscle development
  • Bones grow thicker + deposit calcium salts in response to increased protein
  • Increases metabolic rate
  • Increase red blood cell number indirectly due to increase metabolic rate
  • Increase reabsorption of sodium in distal tubules of kidneys
29
Q

What happens when you give a still-growing child testosterone?

A
  • Rate of bone growth increases markedly, causing a spurt in total body height
  • Causes epiphyses of long bones to unite with shafts of bones at an early age
    [child doesn’t grow to full potential]
30
Q

What is the MOA of testosterone?

A

1) Testosterone is converted to dihydrotestosterone by 5α-reductase which binds with a cytoplasmic “receptor protein”
2) Combination migrates to cell nucleus where it binds with a nuclear protein + induces DNA-RNA transcription
3) Increase in production of proteins

31
Q

Which hormones control the male sexual functions?

A
  • GnRH from the hypothalamus
    [secreted by neurons of the arcuate nuclei of the hypothalamus which terminate in the median eminence of the hypothalamus -> release GnRH into the hypothalamic-hypophysial portal vascular system to the anterior pituitary gland]
  • FSH and LH from the anterior pituitary
32
Q

What is the difference between LH and FSH in relation to GnRH?

A

LH = cyclical + depends on the release of GnRH
[explains why GnRH is known as LH-releasing hormone]

FSH = increases and decreases only slightly when GnRH secretion changes + changes slowly in response to longer-term changes in GnRH

33
Q

Which feedback mechanism does Testosterone secretion fall under?

A

Negative feedback

Explanation: Testosterone causes a decrease in secretion of GnRH from the hypothalamus -> little to no secretion of LH and FSH -> Leydig cells cannot be acted on which inhibits testosterone secretion

34
Q

What MOA do LH and FSH follow?

A

They activate the cyclic adenosine monophosphate second messenger system which activates specific enzyme systems in respective target cells

35
Q

What is the MOA of FSH on spermatogenesis?

A

1) FSH binds with specific FSH receptors attached to the Sertoli cells in the seminiferous tubules
2) Sertoli cells grow and secrete various spermatogenic substances
3) Testosterone diffuse into seminiferous tubules from Leydig cells + alongside FSH initiate spermatogenesis

36
Q

What is the function of Inhibin?

A

Secreted by Sertoli cells, it affects the anterior pituitary gland to inhibit the secretion of FSH + slight effect on hypothalamus to inhibit secretion of GnRH

37
Q

What is the effect of hCG during pregnancy?

A

It acts like LH and if the foetus is male it causes the testes of the foetus to secrete testosterone -> promotes formation of male sexual organs

38
Q

Describe Prostate cancer

A

An abnormal overgrowth of prostate tissue that can cause urinary obstruction

METASTASIS:
- cancerous cells are stimulated to more rapid growth by testosterone

TREATMENT:
- removal of testes so testosterone cannot be formed
- administration of oestrogen’s
or BOTH to slow cancer

39
Q

Describe Hypogonadism in males

A

When the testes of a male foetus are non-functional during foetal life, none of the male sexual characteristic develop in the foetus

Explanation: Female sexual organs develop in the foetus if there are no sex hormones -> but in the presence of testosterone, formation of female sex organs is suppressed and male organs are induced

40
Q

What happens when a boy loses his testes before puberty?

A
  • Infantile sex organs and characteristics throughout life
  • Height is greater than a normal man
    [bone epiphyses is slow to unite - but bones are thin and muscles are weaker]
  • Voice is childlike
  • No loss of hair on the head
  • No normal adult masculine hair distribution
41
Q

What happens when a man loses his testes after puberty?

A
  • Sexual organs slightly get smaller
  • Voice slightly regresses
  • Loss of masculine hair, loss of thick bones, loss of muscle
  • Sexual desires are decreased + ejaculation is rare
    [semen-forming organs degenerate]
42
Q

What is Adiposogenital syndrome/Frohlich syndrome/Hypothalmic eunuchism?

A

Obesity occurring with eunuchism

CAUSE:
Hypogonadism caused by a genetic inability of the hypothalamus to secrete normal amounts of GnRH -> simultaneous abnormality of the feeding centre of the hypothalamus, causing person to greatly overeat

43
Q

What is Erectile dysfunction?

A

Also called “Impotence” is an inability of a man to develop or maintain an erection of sufficient rigidity for satisfactory sexual intercourse

CAUSES:
- Neurological problems (e.g parasympathetic trauma)
- Deficient levels of testosterone
- Drugs
- Underlying vascular disease (caused by uncontrolled hypertension, diabetes and atherosclerosis) -> impaired vasodilation + decreased release of nitric oxide

TREATMENT:
Phosphodiesterase inhibitors (e.g viagra)
[inhibit degradation of cyclic GMP allowing for erection]

44
Q

What are the functions of the Pineal gland?

A
  • Enhancing sex
  • Staving off infection
  • Promoting sleep
  • Enhancing mood
  • Increasing longevity
45
Q

What are the effects of the Pineal gland?

A
  • Controlled by the amount of light or “time pattern” of light seen by the eyes each day
  • Secretes melatonin
  • Secretion of melatonin decreases gonadotropic hormone secretion

PHYSIOLOGY IV (14 decks)

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