Session 7 Flashcards
What are the phases of Coitus?
Excitement phase
Plateau phase
Orgasmic phase
Resolution phase
What happens in the Excitement phase of Coitus?
Arousal by mechanical or psychological stimuli
Blood to erectile tissue in males
Blood engorgement to breast, clitoris and vaginal mucosa in females
What happens in the Plateau phase of Coitus?
The excitement levels off
What happens in the Orgasmic phase of Coitus?
More stimuli is needed
Glandular activity of the vagina occurs
+/- orgasm in females
What happens in the Resolution phase of Coitus?
Males have a physiological refractory period
Females have a psychological refractory period
Vascular changes return to normal
What causes an erection in males?
The parasympathetic nervous system
Vascular changes
What causes vasodilation for Tumescence? (Engorgement of blood)
Inhibition of sympathetic arterial vasoconstrictor nerves –> Vasodilation
Activation of the Parasympathetic nervous system
Activation of non-adrenergic, non cholingeric nerves to arteries - release Nitiric Oxide causing vasodilation
What causes muscle relaxation for Tumescence?(Engorgement of blood)
Post ganglionic parasympathetic nervous system releases Ach which binds to M3 receptors on endothelial cells
Rise in [Ca2+]i leading to activation of Nitiric Oxide synthase making Nitric oxide
NO diffuses into vascular smooth muscle to cause relaxation
NO released from nerves makes cGMP which causes Ca2+ to go into the Endoplasmic reticulum leading to decreased [Ca2+]i
What are the 2 layers of the penis with erectile tissue?
Corpora cavernosa (Rigid fibrous tissue outer layer. Stops blood draining away) Corpus spongiosum (Around urethra so not as rigid)
What can cause erectile dysfunction?
20% = psychological. (Descending inhibition of spinal reflexes)
Tears in fibrous tissue of Corpus cavernosa
Vascular issues eg diabetes
Drugs eg antidepressants, antihypertensives, things blocking NO
How does Viagra treat erectile dysfunction?
It maintains dilation of vessels by inhibiting phosphodiesterase 5 which breaks down cGMP
What is Emission?
Before ejaculation, movement of the ejaculate into the prostatic urethea - sympathetic nervous system (leakage can occur - why withdrawal method is unreliable)
Vas deferens peristalisis (Sympathetic nervous system)
Accessory gland secretions such as the bulbourethral gland
Quickly followed by ejaculation
What occurs in ejaculation?
Spinal and cerebral reflexes cause it, sympathetic nervous system control - L1, L2
1) Contraction of glands & ducts (Smooth muscle)
2) Bladder internal sphincter contracts (Stop semen going into the bladder)
3) Rhythmic striatal muscle contractions (Pelvic floor, ischiocavernosus, bulbospongiosus, hip & anal muscles) Big autonomic response
What is a dry orgasm?
No ejaculate comes out.
Due to the internal sphincter of the bladder not contracting properly so semen goes into the bladder.
Can be tested for by taking a urine sample post coitus
What do you look for in semen samples?
% of sperm swimming forward vigorously (60%)
Volume (2-4ml)
How many sperm per ml (20-200x10[6])
What are the glandular components of semen?
60% = Seminal vesicles. Alkaline, fructose, prostaglandins, clotting factors (Semenogelin) 25% = Prostate gland. Milky, slightly acidic, proteolytic enzymes to breakdown clotting proteins (reliquifying semen in 10-20 mins) citric acid, acid phosphate 15% = Alkaline mucous that lubricates end of penis & urethral lining
What happens on days 7-14 of the menstrual cycle?
Uterine proliferation due to oestrogen
What happens around day 14 of the menstrual cycle?
Ovulation
What happens on days 14-28 of the menstrual cycle?
Uterine secretory phase - Oestrogen & Progesterone
What does the presence of Oestrogen & Progesterone cause?
A thick sticky mucus plus to form (This stays if fertilisation occurs and is shed when labour begins)
What is the mucus like if there is only Oestrogen present?
Abundant
Clear
Non viscous
What is Oxytoxin?
Released during sex to cause rhythmic contractions of the uterus
Aids sperm in their movement
What is Capacitation of sperm?
Further maturation that occurs in the female tract (6-8hrs)
Sperm cell membrane changes to allow fusion with the oocyte cell surface
Tail movement changes from beat to whip like action
Many sperm are needed to breakdown the Zona pellucida (Minimum 299) then one enters
What is the fertile period?
Sperm disposition up to 3 days prior to ovulation to allow sperm time to reach the ampulla
How is the oocyte transported?
The cilia beat
Peristalsis of the fallopian tube
Where does fertilisation occur?
In the Ampulla of the fallopian tube
What does fertilisation require?
Loss of the sperm’s outer shell (Acrosome lost in acrosomal reaction)
Penetration of ovum membrane, fusion of the ova and sperm
Eventual formation and fusion of pronuclei
How does fertilisation occur?
Sperm pushes through the granulosa cells
Proteins on the sperm head bind to ZP3 proteins of the zona pellucida
Binding triggers the acrosome reaction;
- Acrosomal enzyme exposed to the Zona Pellucida
- Hydrolysing enzymes digest path through the Zona Pellucida
- One sperm penetrates, fusion of plasma membranes
- Sperm moves into cytoplasm (Zygote)
- Cortical reaction hardens the Zona Pellucida so polyspermy is blocked
- Egg completes meiosis II
Proniculei, then fusion
Mitosis
What is Cleavage?
Series of metabolic changes and rapid mitotic division
Increased number of cells without growth
Totipotency (Each cell has the potential to grow into a human)
Splitting of this would result in monozygotic twins
What happens to the conceptus in the uterine tube?
Awaits rise in progesterone so the smooth muscle relaxes
Period of cell division to the blastocyst stage
What is the Blastocyst?
Loss of totipotency
Outer trophoblast layer
Inner cell mass which becomes the embryo
Fluid filled cavity
What happens to the conceptus in the uterus?
Floats for 3 days nourished by the intrauterine fluid
Sticky trophoblast adheres to endometrium (hCG released to maintain corpus luteum)
Implantation commences 6 days after ovulation (2/3rds down the posterior wall)
What is on of the risks with Ectopic pregnancy?
There is not a good blood supply to support the embryo
Arteries can be damaged eg ovarian/uterine leading to a haemorrhage
