Male Reproductive System Flashcards
What is role of the testis
Sperm and hormone production
What are the three principle cell types involved in the testis and their roles
- Leydig cells- occupies space between tubules (outside tubules)
- Sertoli Cells- within tubules- starts off spermatogenesis
- Germ Cells- within tubules and lumen- when it gets to lunial surface it becomes sperm (washed away when ejaculated)
Describe the hypothalamic pituitary regulation of LH and FSH in male
GnRH (Gonadotrophin Releasing hormone) neurones in hypothalamus are stimulated
Production of LH and FSH to produce gonadotroph cells in anterior pituitary (systemic circulation)
LH is made by Leydig cells which becomes testosterone (androgens)
FSH is made by sertoli cells which becomes inhibin
Which two hormones in the testicular system have a negative feedback in LH and FSH secretion
Inhibin and Testosterone
What are the effects of androgen (testosterone) mainly before birth
Synthesised in fatal leydig cells in response to maternal hCG to cause descent of testes into scrotum
How is T converted to DHT
5-alpha reductase enzyme
What are the effects of androgen (testosterone) after birth (puberty)
Promotes growth and maturation of reproductive system
Penis enlargement and scrotum enlargement
Scrotum darkening
Enlargement of epididymis, prostate, seminal vesicles
Essential for spermatogenesis
Development of sex drive and controls gonadotrophin secretion
What are the secondary sex characteristics that androgens develop
Promotes muscle growth responsible for male body confirmation:
Increased protein synthesis
Decrease protein degradation
Increase lean:fat ratio
Promotes bone growth at puberty
Induces male pattern of hair growth
Deepening of voice
Skin thickens and sebaceous glands do (acne)
What is the andropause
Decreased testosterone production, reduced testicular androgen response to LH
What are physical changes in the andropause
Loss of muscle mass
Shrinking reproductive organs- penis, testicles, accessory glands
Loss of libido, increased stimulus for erection
Longer refractory period
Osteoporosis
Depression and reduced energy
How does erectile dysfunction occur
Nervousness- performance
Guilty- adultery
Relationship problems
Depression and exhaustion
What are the common physical causes of erectile dysfunction
Deterioration of arteries- common in older men with high blood pressure (atherosclerotic plaque blocks blood flow to penis)
Smoking
Diabetes
Excessive alcohol- whisky dick
Obese and out of condition
Side effects of drugs: anti-hypertensives and anti-depressants
What are the three different regions of the penis called and their anatomy
Corpus caverosum- parallel spongy columns
Central corpus spongiosum (enclosing urethra)
Cavernous sinuses- erectile tissue rich in tiny pool shaped blood vessels- fills with blood during erection
Describe the stages of an erection occurring (4)
- Psychogenic or tactile stimulation triggers the release of Ach (acetylcholine) from parasympathetic nerve endings
- Neuronal nNos is released from cavernous nerve which decreases noradrenaline
- Increased eNOS (endothelial nitric oxide synthase) in the vascular endothelial cells
- Increase of nitric oxide (NO) causes dilation of smooth muscles and increased blood supply into corpus cavernous and corps spongiosum
Describe the biochemical process of an erection
- Ach produced, neuronal nNos stimulates eNos
- NO synthesised diffuses into vascular smooth muscle
- Once inside nitric oxide binds to and activates guanylyl cyclase, converts GTP to cGMP
- cGMP activates protein kinase G
- PKG activation: promotes vascular smooth muscle relaxation via
hyperpolarisation (K+ channels opening)
Endoplasmic reticulum sequestration of Ca2+
Inhibition of Ca2+ channels stops influx
What does calmodulin do and how is it activated
Aids phosphorylation of myosin light chains (MLC)
Activated by free intracellular calcium
Where are MLCs (myosin light chain) found and their roles
- Subunits on myosin heads
2. When phosphorylated, they cross bridge on myosin heads and actin filaments cause cellular contraction
What is the mechanism of action of viagra
- Competitively inhibits enzyme responsible for degradation of cGMP to GMP (phosphodiesterase type 5)
- Stabilisation of cGMP- prolonged action of second messenger
- Greater more sustained dilation of sinusoidal smooth muscle via PKG (needed to reduce free cytosolic calcium ion concentration)
- Engorgement of erectile tissue with blood
What are the common side effects of viagra
Flushing
Headache
Nasal Congestion (vasodilation elsewhere)
What are the less common side effects of viagra
Blurred vision
Loss of hearing
Bladder pain
Dizziness, pain on urination
What is priaprism
Persistent painful erection lasting longer than four hours in absence of sexual desire
What are the two types of priaprism
Ischaemic- no flow
Non-ischaemic- high flow (excess arterial supply)
How do you treat priaprism
Intracavernosal injection of alpha adrenoceptor agonist
What is the function of the prostate gland
Secretion of slightly alkaline prostatic fluid that is mixed with sperm and secretions from other accessory glands
