Lecture 5.2: Coitus & Fertilisation Flashcards
What is the Definition of Sexual Reproduction?
Formation of a unique individual from the gametes (spermatazoon and oocyte) of two other individuals
How many days does spermatogonia to mature spermatozoa take? In what parts of the male reproductive system does this occur?
- c. 74 days
- ~50 days in seminiferous tubules
- ~12-26 days in epididymis
How many spermatozoa made every second?
1000
What are the 3 parts of the epididymis?
- Head (caput)
- Body (corpus)
- Tail (cauda)
What happens in the caput of the epididymis? (2)
- Fluid reabsorption
- Sperm chromatin compaction
What happens in the corpus of the epididymis? (5)
- Protein synthesis
- Vesicles secretion
- Acquisition of progressive sperm motility
- Sperm chromatin compaction
- Defence response
What happens in the cauda of the epididymis? (4)
- Sperm storage
- Sperm chromatin compaction
- Defence response
- Sperm quality control
Pathway of sperm transport to the female reproductive system?
- Through epididymis
- Into urethra (emission)
- Out of the male body (ejaculation)
- Through the female tract
What are the Phases of Sexual Response in Males? (4)
- Excitement phase (erection)
- Plateau phase
- Orgasmic phase (emission and ejaculation)
- Resolution phase (+/- refractory period)
What are the Phases of Sexual Response in Females? (5)
- Excitement phase (blood engorgement and erection:
clitoris, vaginal mucosa, breast and nipples) - Plateau phase
- Glandular activity
- +/- orgasm
- No physiological refractory period
What is Tumescence?
The quality of being swollen, or a swollen part of the body, especially caused by sexual excitement
What Haemodynamic Changes causing Tumescence
- Inhibition of sympathetic arterial vasoconstrictor
nerves - Activation of PNS
- Activation of nonadrenergic, noncholinergic,
autonomic nerves to arteries, releasing NO
How does NO cause smooth muscle relaxation and vasodialation? (5 Steps)
- Endothelial cells stimulated to release NO
- NO also released directly from nerves
- NO diffuses into vascular smooth muscle
- Decreased Ca2+
- Relaxation of smooth muscle (vasodilation)
What are some causes of erectile dysfunction?
- Psychological (descending inhibition of spinal reflexes)
- Tears in fibrous tissue of corpora cavernosa
- Vascular (arterial and venous)
- Drugs
- Factors Blocking NO: alcohol, anti-hypertensives,
diabetes
Viagra causes an erection, what is its MOA?
- Normally, the PDE (phosphodiesterase inhibitors)
breaks down the cGMP into molecules that cannot
cause erections - By inhibiting the breakdown of cGMP, Viagra leads to
more cGMP - PDEs cause reductions in the needed chemical in the
penis, and Viagra blocks the PDE to prevent this from
happening
How does Emission of Semen occur?
- Movement of ejaculate into prostatic urethra (leakage)
- Under sympathetic control
- Vas deferens peristalsis
What gland add secretions to semen? (3)
- Prostate
- Seminal Vesicle
- Bulbourethral Glands (Cowper’s Glands)
What percentage of Glandular Components of Semen come from Seminal Vesicles?
60% volume
What kind of fluid do the seminal vesicle secrete? What does it contain?
- Alkaline fluid (neutralises the acid: male urethra &
female reproductive tract) - Fructose
- Prostaglandins
- Clotting Factors
- Semenogelin
What percentage of Glandular Components of Semen come from Prostate?
25% volume
What kind of fluid does the Prostate secrete? What does it contain?
- Milky, slightly acidic fluid
- Proteolytic enzymes (breakdown clotting proteins, re-
liquefying semen in 10-20 minutes ) - Citric Acid
- Acid Phosphatase
How much of the Glandular Components of Semen come from Bulbourethral Glands (Cowper’s Glands)?
Very small volume
What kind of fluid do the Bulbourethral Glands (Cowper’s Glands) secrete? What does it contain?
- Alkaline fluid
- A mucous that lubricates the end of the penis and
urethral lining
What is the Mechanism of Ejaculation?
- Spinal (& cerebral) reflex
- Sympathetic Nervous System Control (L1, L2)
1. Contraction of glands and ducts (smooth muscle)
2. Bladder internal sphincter contracts
3. Rhythmic striatal muscle contractions (pelvic floor,
ischiocavernosus, bulbospongiosus, hip and anal muscles)
What is the medical term for low sperm count?
Oligozoospermia
What is the site of fertilisation?
Fallopian Tubes
How many sperm per ejaculation?
200-300 million per ejaculation
How many sperm reach site of fertilisation?
300 reach fertilisation site
Vagina Histology (inner to outer)
- 3 layered fibromuscular canal (mucosa, smooth
muscular layer [SM], adventitia) - Highly-vascular lamina propria (LP), which is elastic
fibre rich but not gland-bearing - Glycogen producing non-keratinised stratified
squamous epithelium (E)
Endocervix Histology
Cervical canal with simple columnar epithelium and
mucous glands (but no spiral arteries)
Exocervix Histology
- Stratified squamous non-keratinised epithelium
- Squamocolumnar junction (SCJ) can be located at any
point across the cervix - The transformation zone adjacent to the SCJ is where
majority of neoplasms originate
Uterus Histology (out to in) (3)
- Perimetrium (serosa mainly)
- Myometrium
- Endometrium (composed of stratum basalis &
functionalis [which is made of stratum spongiosum &
compactum])
What are the sections the Endometrium is composed of?
- Stratum basalis
- Stratum functionalis [stratum spongiosum & stratum
compactum]
What are the parts of the Fallopian Tube(from ovaries to uterus)? (4)
- Fimbriae
- Infundibulum
- Ampulla
- Isthmus
What cells in the ampulla of the fallopian tubes secrete nutrient material for the ovum?
Peg Cells
Further maturation of the sperm occurs during transport through the female reproductive tract, how long does this take?
6-8 hours
Survival of fertile gametes after release: Spermatozoa
48 - 72hrs after ejaculation
Survival of fertile gametes after release: Oocytes
6 – 24 hr (max) after ovulation
How is oocyte transported through the fallopian tube? (2)
- Beating cilia
- Peristalsis of Fallopian tube
What is the Fertile Period?
Sperm deposition up to 3 days prior to ovulation or day
of ovulation
What part of the sperm is lost during fertilisation?
Loss of sperm outer shell (acrosome) during the
acrosome reaction
What parts of the ovum does the sperm break through during fertilisation?
- Penetration of granulosa cell layers
- Corona radiata
- Zona pellucida
- Ovum membrane
What 2 enzymes are released from acrosome?
- Hyaluronidase- breaks down hyaluronic acid in which
the cells of the cumulus oophorus, that surround the
oocyte, are embedded. - Acrosin- a protease that breaks down ZP proteins
Oocyte Activation (6 Steps)
- Fusion of gamete membranes triggers Ca2+ release
from SER - Cortical reaction (block to polyspermy)
- Egg completes meiosis II (second polar body created)
- Pronuclei formed (2 sets of chromosomes)
- Pronuclei fusion (diploid zygote)
- Embryonic mitosis cleavage
Days 1-6 of fertilisation
Day 1: Fertilisation, zygote
Day 2: 4-cell stage
Day 3: Morula
Day 4: Early blastocyst
Day 6: Implanting blastocyst
