Flashcards in Coitus Deck (33):
What constitutes 'normal' semen?
Normal volume is 2-4 ml
20-200 x 10^6 sperm
>60% sperm swimming forwards vigorously
What is contained in secretions of the seminal vesicles?
Clotting factors including fibrinogen
What is in prostatic secretions and why?
Milky, slightly acidic
Proteolytic enzymes to break down clotting enzymes to re-liquefy sem in 10-20 mins
Citric acid and phosphatase - energy source
Secretion of the bulbourethral glands?
Small amount, alkaline
A mucous for lubrication of the end of the penis and urethral lining
What is emission?
The movement of ejaculate into the prostatic urethra before ejaculation
How does emission occur?
Peristalsis of the vas deferens and secretions from the seminal vesicles
What are the physiological processes of erection?
-tactile (sensory afferents of penis and perineum)
-somatic and autonomic via pelvic nerve (PNS) and pudendal (somatic)
How much sperm is there per ml?
20-200 x 10^6
What changes happen to the autonomic nervous system in the haemodynamic changes in the process of erection?
Inhibition of sympathetic arterial vasoconstrictor nerves and activation of the parasympathetic nervous system
Which nerve is one of the few where an increase in parasympathetic stimulation causes vasodilation?
What happens when there is an increase in parasympathetic stimulation in the pelvic nerve?
Release of acetylcholine to M3 receptors on epithelial cells
Rise in calcium concentration which activates nitric oxide synthase (NOS)
Nitric oxide (NO) is produced
Activates non-adrenergic and non-cholinergic nerves to artery releasing NO
Diffuses in and causes relaxation of vascular smooth muscle
How does nitric oxide relax smooth muscle?
NO increases formation of cGMP so calcium is taken up into intercellular stores
Decrease in calcium conc means less actin-myosin cross-bridges can be formed -> muscle relaxation
Which arteries vasodilate during erection and what does this do?
The central arteries in the corpa cavernosa straighten, which enlarges their lumen and allows blood to flow in and dilate cavernous spaces
What compresses the veins draining the corpa cavernosa?
Bulbospongiosus and ischiocavernosus muscles - impedes return of venous blood
Causes of erectile dysfunction?
Psychological - descending inhibition of spinal reflexes
Tears in fibrous tissue of the corpus cavernosa
Vascular causes - most common
Factors which block NO
How does Viagra work?
Inhibits breakdown of cGMP so that an erection is maintained
What physiological changes happen in a female to facilitate coitus?
Swelling and engorgement of external genitalia
Internal enlargement of the vagina
What is the difference between mucus produced due to oestrogen and produced due to progesterone and oestrogen?
Oestrogen - abundant, clear, non-viscous
Progesterone and oestrogen - thick, sticky mucous plug
Which nerve roots control ejactulation?
L1 and L2
Mechanism of ejaculation?
Contraction of glands and ducts (smooth muscle)
Internal sphincter of bladder contracts
Rhythmic striatal muscle contractions (pelvic floor, ischiocavernosus, bulbospongiosus, hip and anal muscles)
What happens to the sperm after ejaculation?
Coagulates due to fibrinogen
10-20 mins later, semen re liquefies due to enzymes from prostatic secretions
Vast majority don't enter cervix, lost by leakage
Those that do, travel 15-20cm to reach uterine tube - hours
Why does semen coagulate?
Prevents sperm being lost from the vagina
What is transport of sperm a result of?
Their own propulsive capacity
Fluid currents caused by action of ciliates cells in the uterine tract
What happens to the sperm as they pass though the uterus and uterine tube?
Undergo a series of maturational changes - capacitation and acrosomal reaction
How is the acrosomal reaction and capacitation induced?
Influx of calcium and a rise in cAMP in spermatozoa
What is capacitation?
Further maturation of sperm in the female repro tract over 6-8 hours
Sperm cell membrane changes to allow fusion with oocyte cell surface by removal of glycoprotein coat
Tail movement changes from a beat to a whip-like action
Sperm becomes responsive to signals from the oocyte
What is the acrosomal reaction?
When capacitation sperm contact the oocyte zona pellucida, the membranes fuse which starts the reaction
Acrosome swells and liberates its contents by exocytosis
Proteolytic enzymes and further binding facilitates penetration of the zona pellucida by sperm
Takes around 15 mins
What division has the primary oocyte undergone by the time of ovulation?
Has completed its first division to form a secondary oocyte
What is produced after the first meiotic division of the primary oocyte?
A secondary oocyte with the haploid number of chromosomes and bulk of the cytoplasm
First polar body with the remaining haploid number of chromosomes
What is the secondary oocyte surrounded by before it is released from the follicle?
Surrounded by follicular cells which form the cumulus
Embedded in a gelatinous matrix
What happens when the sperm penetrates the cytoplasm of the ovum?
The nuclei fuse
Forms the zygote
Then divides by mitosis to form the morula
Then a hollow structure called the blastocyst
All while being transported down the uterine tube
How long does it take for the blastocyst to reach the uterine cavity and how long does it take to implant
Implants after about a day in the cavity