7 - Sexual Reproduction in Humans (C2) Flashcards
Doesn't include spermatogenesis and oogenesis
What does the seminal vesicle do in the male reproductive system?
During ejaculation it adds alkaline mucus, containing fructose and amino acids, to nourish the sperm
What does the vas deferens do in the male reproductive system?
Transports sperm to the urethra via a peristaltic wave during ejaculation
What does the prostate gland do?
- Produces a zinc containing alkaline secretion which neutralises any urine left in the urethra and acidic vaginal secretions
- Aids in sperm mobility
What does the urethra do in the male reproductive system?
Transfers urine and semen out of the penis
What does the epididymis do in the male reproductive system?
It’s where sperm are collected and mature
What does the seminiferous tubule do in the male reproductive system?
It’s the site of sperm production
What does the testicle do in the male reproductive system?
Produces male gametes (spermatozoa)
What is the scrotum and what is its function?
- It’s an external sac that holds the testes outside of the body
- This provides an optimum temperature for sperm production of 35 degrees
What is the penis and what is its function?
- An organ containing blood filled erectile tissue
- Passes semen into the vagina
What is the ovary and what is its function?
- Female sex organ (gonad)
- Starts gamete production and releases secondary oocytes
- Secretes oestrogen and progesterone
What is the role of the uterus wall?
- Retains the foetus
- Contracts during birth (controlled by oxytocin - positive feedback)
What is the cervix and what does it do?
- A muscular ring at the neck of the uterus
- Closes the entrance to the uterus
- Dilates during birth from resting diameter of 2mm
What is the function of the fallopian tube/oviduct?
- Ciliated epidermis wafts the oocyte/embryo to the uterus
- Site of fertilisation
What is the endometrium and what does it do?
- Mucus rich membrane
- Rich in blood capillaries
- Shed monthly
- Provides nutrients to implanted embryos
What is the vagina?
- Muscular tube
- Site of sperm deposition
What are the 5 major roles of the placenta?
- Production of oestrogen and progesterone
- Exchange of O2/CO2, nutrients/waste
- Barrier to high blood pressure, blood borne pathogens and toxins in maternal blood
- Allows maternal antibodies to protect the foetus
- Prevents antibodies attacking the foetus
What are problems the placenta can cause?
- The immune system may attack the placenta or foetus due to Rhesus incompatibility
- Small viruses or toxins are transferred across the placenta e.g. rubella, alcohol
What is the function of leydig cells?
Secrete testosterone
What is the amnion?
Fluid filled sac which eventually surrounds and protects the embryo from mechanical damage
What does amniotic fluid contain?
- Foetal skin cells
- Can be sampled to check for chromosome abnormalities
What is the acrosome reaction?
- Triggered when sperm bind to a protein
- Acrosome membranes rupture and hydrolytic enzymes are released
- Acrosin enzyme digests the zona pellucida
What happens as the sperm enters the egg?
- Proteins in sperms cell membrane bind to the oocyte membrane and they fuse
- Sperm nucleus enters
- Entry of the head of the sperm causes the egg to complete meiosis and the 2 haploid nuclei fuse to form a zygote
What is the cortical reaction?
- Calcium ions enter the egg and vesicles of cortical granules move to and fuse with the oocyte membrane
- Zona pellucida lifts and hardens, forming a fertilisation membrane
- Binding proteins change shape
How is polyspermy prevented?
Membrane polarity changes, due to cortical reaction
What is the role of HCG?
- Maintains the corpus luteum and prevents it being broken down
- Maintains progesterone production
Why are there high levels of oestrogen and progesterone in the blood plasma until the end of the pregnancy?
This inhibits the secretion of:
- FSH, so no more follicles mature
- LH, so ovulation is not possible
- Prolactin, so no milk is made
- Oxytocin, so the myometrium and muscles in the milk ducts don’t contract
What does oestrogen stimulate during pregnancy?
- The growth of the uterus
- The growth of the mammary glands
What are the functions of the amniotic fluid?
- Maintains foetus’s temperature
- Provides lubrication
- Contributes to lung development
- Allows movement so muscles and bones function before birth
- Acts as a shock absorber
What is the role of oestrogen?
- Rebuilds the endometrium
- Inhibits FSH secretion
- Stimulates LH production
What does the alkaline prostate fluid do?
- Maintains sperm mobility
- Provides nutrients, including fructose, amino acids and zinc
- Neutralise the acidity of urine in urethra
- Neutralise the acidity of vaginal tract
What do Sertoli cells do?
Secrete a fluid which nourishes spermatids and protects them from male’s immune system
What does testosterone do?
Has roles in sperm formation and maturation, and the development of male secondary sexual characteristics
What are the 3 layers of the uterus wall?
- Perimetrium - thin layer around outside
- Myometrium - muscle layer
- Endometrium - innermost layer
What does the endometrium do?
Builds and sheds blood in a monthly cycle
Why does the middle piece of sperm have lots of mitochondria?
To provide ATP for movement
What does the corpus luteum do if fertilisation occurs and what does it do if it doesn’t?
- Does -> Produces hormones
- Doesn’t -> Regresses
What do cortical granules do?
Prevent the entry of more than 1 sperm
What is capacitation?
The removal of cholesterol and glycoproteins from cell membrane over acrosome in sperm head, which increases its fluidity and allows acrosome reaction to occur
What events make up the fertilisation sequence?
- Sperm surround secondary oocyte
- Capacitation
- Acrosome reaction
- Sperm head entry
- Cortical reaction
- Meiosis II
- Mitosis
What is cleavage?
A sequence by which the embryo divides by mitosis, as it moves down the oviduct
What is implantation?
The sinking of the blastocyst into the endometrium
What are trophoblasts?
Cells forming the outer layer of the blastocyst
How is a concentration gradient ensured between the maternal and foetal blood?
By a counter-current flow
What does FSH stand for?
Follicle stimulating hormone
What is Rhesus disease in a foetus?
The destruction of its blood cells by antibodies made by a Rhesus negative mother against blood cells of a Rhesus positive foetus
What is the role of FSH?
- Stimulates development of primary follicles
- Stimulates Graafian follicle development
- Stimulates production of oestrogen
What is the role of LH?
- Induces ovulation
- It’s high conc on day 14 causes the Graafian follicle to release the secondary oocyte
- Has a positive feedback effect on FSH
What is the role of FSH?
- Stimulates development of primary follicles
- Stimulates production of oestrogen
What is the role of LH?
- Induces ovulation
- It’s high conc on day 14 causes the Graafian follicle
What does progesterone do?
- Maintains the endometrium
- Inhibits oxytocin
What does oxytocin do?
- Causes contractions of myometrium in uterus wall so foetus can be pushed out through cervix
- These contractions stimulate secretion of more oxytocin by positive feedback
What does progesterone do?
Maintains the endometrium
What does prolactin do?
Stimulates glandular tissue in mammary glands to synthesise milk
