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Flashcards in Male reproduction Deck (48)
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1
Q

List 3 processes which occur in the male reproducive system

A
  1. Gametogenesis
  2. Secretion of sex hormones (androgens, especially testosterone)
  3. Delivery of sperm to female tract
2
Q

Name 2 processes that occur in the testis

A
  1. Sperm reproduction
  2. Hormone production
3
Q

Describe the structure of the male reproductive system

A

(https://s3.amazonaws.com/brainscape-prod/system/cm/203/781/084/a_image_thumb.PNG?1482744922)

4
Q

What is the vas deferens?

A

The duct which conveys sperm from the testicle to urethra

5
Q

What are the seminiferous tubules?

A
  • Found in testes
  • Location of meiosis and the subsequent creation of male gametes (sperm)
6
Q

Name 3 cells found in the testis

A
  1. Leydig cells (outside s. tubules)
  2. Sertoli cells (within s. tubules - epithelium)
  3. Germ cells (within s. tubules and lumen)
7
Q

How are FSH & LH regulated by the hypothalamus and pituitary in males?

A
  1. GnRH secreted from hypothalamus
  2. GnRH stimulates secretion of FSH and LH
  3. FSH and LH produced by gonadotroph cells in the anterior pituitary
8
Q

How does LH act in the testis?

A
  • LH stimulates the Leydig cells within the testes/s.tubules

→ produces testosterone

  • This encourages sperm production and leads to secondary sexual characteristics
9
Q

What is the role of FSH in the testis?

A
  • FSH stimulates primary spermatocytes to undergo the first division of meiosis

​→ forming secondary spermatocytes

leading to the maturation of sperm cells

  • Also acts on Sertoli cells = inhibin
10
Q

How is FSH regulated by negative feedback?

A
  1. FSH causes the production of Inhibin
  2. Inhibin inhibits FSH production by having a negative feedback effect on the anterior pituitary
11
Q

How is LH regulated by negative feedback?

A
  1. LH causes production of testosterone
  2. Testosterone has a negative feedback effect on the hypothalamus and anterior pituitary

inhibiting GnRH and so LH production

12
Q

What are the effects of testosterone (androgens) before birth?

A

Testosterone is synthesised by fatal Leydig cells in response to maternal hCG

  • It masculinises the external genitalia
  • Promotes descent of testes into scrotum
13
Q

What are the effects of testosterone (androgens) after birth?

A
  • Testosterone production very low until puberty
  • Around puberty, LH production by the pituitary is initiated

stimulates testosterone output by testis

14
Q

What are the effects of testosterone on sex-specific tissues? (i.e. after puberty)

A
  • At puberty, testosterone promotes growth and maturation of reproductive system

→ penis & scrotum enlargement

→ scrotum darkening

→ Enlargement of epididymis, prostate, seminal vesicles

  • Essential for spermatogenisis
  • Maintains reproductive tract throughout adulthood
15
Q

List 2 reproductive effects of testosterone

A
  1. Development of sex drive (libido) at puberty
  2. Control of gonadotrophin secretion (via negative feedback)
16
Q

List 5 effects of androgens on secondary sex characteristics

A
  1. Promotes muscle growth responsible for male body conformation (increases protein synthesis and lean:fat ratio, decreases protein degradation)
  2. Promotes bone growth at puberty then closure of epiphyses (ends of bone)
  3. Induces male pattern of hair growth (i.e. beard)
  4. Causes deepening of voice
  5. Skin and sebaceous glands thicken (acne)
17
Q

What is the andropause?

A
  • “male menopause”, age 48-70
  • Decreased testosterone production
  • Reduced testicular androgen response
  • However sperm production continues (unlike menopause)
18
Q

List 4 physical changes caused by the andropause

A
  1. Loss of muscle mass
  2. Shrinking of reproductive organs - penis, testis, accessory glands
  3. Loss of libido, increased stimulus needed for erection, longer refractory period
  4. Osteoporosis
19
Q

List 2 mental changes caused by the andropause

A
  1. Depression
  2. Reduced energy
20
Q
A
21
Q

List 5 common psychological causes of erectile dysfunction

A
  1. Nervousness
  2. Guilt - adultery etc
  3. Relationship problems
  4. Depression
  5. Exhaustion
22
Q

List up to 6 common physcial causes of ED

A
  1. Deterioration of arteries - common in older men, including those with high BP
  2. Diabetes
  3. Smoking
  4. Excessive alcohol
  5. Obese/out of condition
  6. Side effects of certain drugs - e.g. anti-hypertensives, anti-depressants
23
Q

What are the 3 different regions of the erectile tissue?

A

1. & 2. Pair of parallel spongy columns = corpus cavernosum

3. Central corpus spongiosum enclosing urethra

24
Q

What are the cavernous sinuses?

A
  • Pool-shaped blood vessels
  • Erectile tissue rich in cavernous sinuses
  • Fill with blood during an erection
25
Q

Summarise the process behind an erection

A
  1. Sympathetic and parasympathetic nerves innervate blood vessels and sinusoids in erectile tissue
  2. Psychogenic and/or tactile stimulation triggers:
  • increased acetylcholine release (parasympathetic)
  • increased nNOS release
  • Decreased noradrenaline release (sympathetic)
  1. Leads to increased NO = dilation of smooth muscle of arterioles and sinusoids within erectile tissue
  2. Increase in blood flow in the corpus cavernosum and corpus spongiosum
  3. Erection
26
Q

Describe the biochemical process of erection in detail

A
  1. ACh and nNOS (neuronal) are released from the cavernous nerve (in penis)
  2. This stimulates the production of eNOS (NO synthase) within the vascular endothelial cells
  3. NO is synthesised and diffuses into the surrounding vascular smooth muscle
  4. Once inside, NO binds to and activates guanylyl cyclase which converts GTP into the second messenger cGMP
  5. cGMP activates its dependent protein kinase - PKG
  6. PKG activation promotes vascular smooth muscle relaxation (to allow vasodilation) by:
  • Hyperpolarisation (by opening K+ channels)
  • Endoplasmic reticulum sequestration of Ca2+
  • Inhibition of Ca2+ channels, stopping influx
  1. Free intracellular calcium binds to and activates calmodium (protein)
  2. Calmodium aids phosphorylation of myosin light chains (MLC)

MLCs = sub-units found on myosin heads - when phosphorylated they cross-bridge the mysoin heads and actin filaments = cellular contraction

  1. Therefore decrease in cytosolic calcium initiated by PKG results in vascular smooth muscle relaxation

ERECTION

27
Q

What is the chemical name for viagra?

A

Sildenail citrate

28
Q

What is the mechanism of action of Viagra?

A
  1. Sildenafil competitively inhibits phosphodiesterase type 5 (PDE5) = the enzyme responsible for the degradation of cGMP to GMP
  2. Stabilisation of cGMP = prolonged action of second messenger
  3. Therefore greater, more sustained dilation of sinusoidal smooth muscle via PKG-dependent reduction in free cystolic calcium ion concentration
  4. Engorgement of erectile tissue with blood
29
Q

List 4 common side effects of sildenafil citrate

A
  1. Flushing
  2. Headache
  3. Nasal congestion
  4. Stomach discomfort after meals

1, 2 & 3 due to the vasodilation necessary for mechanism of action

30
Q

List 4 less common side effects of sildenafil citrate

A
  1. Blurred vision, loss of hearing
  2. Bladder pain
  3. DIzziness
  4. Pain on urination
31
Q

What is Priapism?

A

Persistent, painful erection lasting longer than 4 hours

→ In absence of sexual stimulation/desire

32
Q

What are the 2 types of Priapism?

A
  1. Ischemic (no-flow) - obstruction in venous drainage
  2. Non-ischemic (high-flow) - excess arterial supply
33
Q

How should Priapism be treated?

A
  • Medical attention should be sought immediately
  • Delayed treatment (especially ischemic type) can cause damage to erectile tissue and irreversible ED
  • Treatment may involve intracavernosal injection of α-adrenoceptor agonist (e.g. phenylephrine)
34
Q

Name another use of Sildenafil

A

Treatment of pulmonary arterial hypertension (under name Revatio)

Reduces BP by widening blood vessels in the lungs

35
Q

List 3 contra-indications of Viagra

A
  1. Low BP
  2. CV disease
  3. Recent stroke
36
Q

What is the prostate gland?

A
  • Walnut-sized muscular gland surrounding the urethra, just below the bladder
  • Secretes (gland) milky alkaline prostatic fluid
  • During orgasm, muscular contractions of prostate propel prostatic fluid into urethra
  • Here it is mixed with sperm and secretions from other accessory glands
  • = Ejaculation
37
Q

What is Benign Prostatic Hyperplasia (BPH)

A

Enlargement of prostate - restricts urethra

Symptoms of BPH:

  • Hesitant, interrupted, weak urine stream
  • Urgency and leaking/dribbling
  • More frequent urination, especially at night
  • 50% of 60 year old men have BPH symptoms
38
Q

How is BPH treated?

A
  • Alpha-adrenoceptor blockers
  • 5-alpha-reductase inhibtors
  • Minimally invasive surgery
39
Q

How do alpha-adrenoceptor blockers work to treat BPH?

A
  • Relax muscle fibres within prostate - reducing obstruction to urine flow
  • Do not reduce size of prostate
  • e.g. tamsulosin, terasozin
  • Occassional side effects - dizzines (postural hypotension), heache, drowsiness
40
Q

Why should Viagra be used with caution in men talking alpha-adrenoceptor blockers?

A

The combination may increase the risk of fall in blood pressure

= dizziness, fainting

41
Q

How do 5-alpha-reductase inhibitors work?

A

Inhibit the growth of the prostate and reduce size of gland

e.g. finasteride

42
Q

List 4 risk factors for prostate cancer

A
  1. Age - risk increases with age, mostly in over 50s
  2. Family history - 2.5x more likely if father or brother has been diagnosed
  3. Ethnicity - Afro-Caribbeans 3x more likely to be diagnosed with prostate cancer than whites
  4. Diet - typical western diet increases risk (high in saturated animal fats and red meat)
43
Q

What are the symptoms of prostate cancer?

A

Similar to BPH (in early stages):

  • Hesitant, interrupted, weak urine stream
  • Urgency and leaking/dribbling
  • More frequent urination especially at night
44
Q

How is prostate cancer diagnosed?

A

Tests by GP:

  • Urine test to rule out infection
  • Then blood test to measure PSA (Prostate Specific Antigen)
  • DRE (Direct Rectal Examination)

Hospital tests:

  • TRUS (Trans-Rectal Ultra Sound) guided biopsy
  • CT scan
  • MRI scan
  • Bone scan with or without X-rays
45
Q

What stages can prostate cancer be at?

A
  1. Localised (only affecting prostate)
  2. Locally advanced
  3. Advanced (metastasis - typically to bone)
46
Q

How is Localised Prostate Cancer treated?

A
  • Active surveillance - treatment started only if/when necessary

→ Radiotherapy

→ Surgical prostatectomy

47
Q

How is Locally Advanced or Advanced PC treated?

A
  • Hormone therapy
  • Tumour growth often androgen-dependent so aim is to block androgen production or action
  • Can also be achieved by surgical castration
48
Q

How does hormone therapy work to treat locally advanced/advanced PC?

A
  1. Down-regulate GnRH receptors to block LH (and androgen) secretion
  2. Block androgen synthesis directly
  3. Block androgen receptors