7.1 Coitus and Fertilisation Flashcards
Where are sperm produced?
Seminiferous tubules of testes
What are the main constituents of sperm?
60% from seminal vesicles:
- Alkaline fluid (neutralise urethra acid)
- Fructose (ATP)
- Prostaglandins (Increased motility)
- Clotting factors (coagulation agent)
20% prostate:
- Proteolytic enzymes
- Citric acid (ATP)
- Zinc
- Phosphatase
2-5% Sperm
200-500 million
5% bulbourethral (Cowper’s) glands
- Mucous for lubrication
Alkali - netralise acid in distal urethra
What is assessed in semen analysis?
Volume (2-4ml)
Sperm count (200-500 million)
Motility
Morphology
What is emission? Nervous system involved?
Movement of ejaculate in prostatic urrethra before ejaculation.
Due to vas deferens perstalsis and sminal vesicle secretion.
Sympathetic (thoracolumbar)
Describe what occurs in emission.
Stimulation of thoracolumbar sympathetic reflex
Contracitno fo smooth muscle in ductus deferens ampulla, seminal vesicles and prostate.
Internal and external urethras contract.
Semen is pooled in urethral bulb.
What are the phases of coitus?
Excitement
Plateau
Orgasmic
Resoluation
Stimulation of what nerves cause erection? NS?
Somatic an autonomic efferents Limbic system Pelvic nerve (parasympathetic) Pudendal nerve (somatic)
Parasympathetic NS
Describe the physiological process in erection of penis.
Inhibition of sympathetic arterial vasoconstrictor nerves.
Activation of parasympathetic NS - pelvic nerve
Increase in parasympathetic stimulation
ACh –> M3 receptors on endothelium
Rise in Ca2+
Activation of Nitric Oxide Synthase
Formation of NO
NO diffuses into and causes relaxation of vascular smooth muscle - vasodialtion
Increased NO
Increased formation of cGMP
Ca2+ taken up into intracellular stores
Reduced Ca2+ leads to less actin-myosin cross bridges -> SM relaxes
Blood fills copra cavernosa helicine arteries when they straighten.
Blood –> cavernous spaces in the corpora of the penis
Corpus spongiosum dilates but not as much.
Bulbospongiosus and sichiocavernosus muscles compress veins egressing from corpora cavernosa, impeding venous return.
Corpa cavernosa becoem engorged causing erectile bodies to become turgid and erection occurs.
What factors cause erectile dysfunction?
Psychological:
Descending inhibition of spinal reflexes
Tears in fibrous tissue of corpora cavernosa
Vascular:
Arterial and venous
(Most common)
Factors blocking NO
Alcohol
Diabetes
Anti-hypertensives
Endocrine
Diabetes
NEuro
How does viagra work??
Inhibits breakdown of cGMP, increasing penile blood flow and maintaining erection.
What happens in the male plateau phase?
Activation of sacrospinous reflex
Contraction of ischiocavernosus (compression of crus penis impedes venous flow0
Venous engorgement
Rise in intracavernosus pressure –> Decreased arterial inflow.
Stimulation of secretion from accessory glands.
What NS and roots cause ejaculation?
Spinal reflex
SNS
L1, L2
What occurs in ejaculation?
- Contraction of glands and duct smooth muscle
- Bladder internal urethral sphincter contracts to prevent semen entering bladder.
- Rhythmic contractions of striatal muscles:
Filling of the internal urethra stimulates pudendal nerve –> contrition of genitals and pelvic floor, ischiocavernosus, bulbospongiosus, hip, anal muscles. - Explsion of semen.
What occurs in male resolution?
Activation of thoracolumbar sympathetic pathway.
Contraction of smooth arteriolar muscle in corpora cavernosa.
Increased venous return
Detumescence and falccidity
Followed by refractory period.
What is the physiological process in the female excitement phase?
Inhibition of sympathetic stimulation. Parasympathetic stimulation via pelvic nerve leading to vasocongestion and vaginal lubrication. Clitoris engorges with blood Swelling and engorgement of external genitalia. Internal enlargement of vagina Uterus elevates Increase muscle tone, heart rate and BP Cervical mucus
What is the function of cervical mucous? How does this change with hormones?
Facilitates sperm survival and transport:
Alkalinity and low viscosity.
Oestrogen - abundant, clear, non-viscous
O&P - thick, sticky mucous plug. Prevent sperm entry
What is the most common form of sexual dysfunction?
Arousal
Describe the types of arousal dysfunction.
Hypoactive - little interest in sex Aversion - revulsion or fear of sex Hyperactive Nymphomaniac Persistent recurrent inability to attain or maintain lubrication.
Describe what occurs in the female plateau phase.
Further increase in muscle tone, heart rate and BP.
Clitoris withdraw under hood
Bartholin’s gland secretion lubricates vestibule
Uterus elevated.
Outer 1/3 vagina forms orgasmic platform.
Describe the female orgasm
Orgasmic platfor (lower 1/3 of vagina) contracts rhythmically 3-15 times.
Uterus contracts, anal sphincter contracts
Clitoris udner hood
No refractory period.
Describe the female resolution phase.
Clitoris descends
Labia return to unaroused size and colour
Uterus descends
Vagina shortens and narrows back to unaroused state.
Breasts reduce in size, reduced size of areola
What are the changes in coitus with age in females?
Reduced desire. Reduced vasocongestion response Vaginal and urethral tissue lose elasticity. REduced expansion of vagina More rapid resolution.
What happens following deposition of sperm in vagina?
Seme coagulates due to clotting factors from seminal vesicles.
This prevents sperm being physically lost.
10-20 minutes later it reliquaries by the action of proteolytic enzymes from prostate.
Most sperm do not enter the cervix and are lost by leakage.
Ones that do travel 15-20cm tot he uterine tube.
What leads to transport of sperm
Their own propulsive capacity
Fluid currents caused by action of ciliated cells in uterine tract.
