U4 Sexual reproduction in humans Flashcards
What parts to both male and females have?
- A pair of gametes- producing organs
- A system of ducts
- Structures of copulation
What is the process called which men produce sperm?
spermatogenesis
Where are the testes found?
Hanging in a sac external to the body called the scrotum
What does the prostate gland do?
Secretes a white milky fluid that neutralises the acidity of any trace of urine and helps protect the sperm from acidic secretions in the female body
What does the seminal vesicle do?
Secretes a thick, clear fluid that nourishes the sperm.
What do the testes do?
Produce sperm
What does the epididymis do?
Transports and stores the sperm
What does the vas deferens do?
Carry the sperm from the epididymis to the urethra where it leaves the body
What does the urethra do?
Where urine and sperm exit the male body
What does the ovary do?
Structures around 2.5cm long containing small sac like structures called follicles produces the egg
What do the Fallopian tubes do?
Passage for the egg and sperm to meet and for a fertilised egg to travel up to the uterus
What does the penis do?
Responsible for transferring sperm into the female during sexual intercourse
What is the function of the uterus?
Nourish the developing fetus prior to birth
What is the function of the Endometrium?
Layer of cells lining the uterus that is rich in blood vessels
What is the function of the cervix?
It’s a passage that allows fluids to flow in and out of the uterus
What is the function of the vagina?
Lined with smooth muscles and epithelium that secretes mucus. It receives the sperm and a passage exit for the body
What is spermatogenesis?
The production and development of sperm cells
Where does spermatogenesis take place?
It takes place in the seminiferous tubules
What two types of cells do the seminiferous tubules contain?
- Germ cells-which undergo the two divisions of meiosis to form spermatozoa
- Sertoli cells which act as nurse cells enduring that the germ cells have adequate nourishment
What are the stages of Spermatogenesis?
- Germinal epithelium cells are diploid (2n). They divide by mitosis to make diploid spermatagonia and more Germinal epithelium cells
- Spermatogonia divide many times by mitosis and enlarge, making diploid primary spermatocytes and more spermatogonia.
- Primary spermatocytes undergo meiosis 1, making secondary spermatocytes.
- Secondary spermatocytes undergo meiosis ll making haploid spermatids.
- Spermatids mature into spermatozoa or sperm
How is spermatozoa production regulated?
Leading cells (interstitial cells) regulate spermatazoa via sec hormones (testosterone in the presence of luteinizing hormone) These leydig cells are found between the seminiferous tubules and the testes.
Where does Oogenesis take place?
In the ovaries
Where does the development of oocytes take place?
It’s situated in the outer region of the ovary
What happens to the oocytes at puberty?
A regular cycle starts to take place regulated by hormones. FHS (follicle stimulating hormone) stimulates the cells around the follicle to multiple.
What hormone does a maturing follicle secrete?
Oestorgen, it inhibits the secretion of FHS to ensure only one follicle developed at a time
What hormone triggers ovulation?
LH (luteinizing hormone) triggers ovulation.
What is the remains called of an unfertilised follicle called?
Corpus luteum
What is released if fertilisation occurs?
Progesterone
Give a brief summary of Oogenesis
Stage 1:
- Before birth, the diploid Germinal epithelium cells divide by mitosis making diploid oogonia and more epithelium cells
Stage 2:
Oogonia divide many times any mitosis and make diploid primary oocytes at prophase l in the ovaries
Stage 3:
Germinal epithelium cells divide to form diploid follicle cells, which surround the primary oocytes making primary follicles
Stage 4:
From puberty, hormones stimulate the primary follicle development. Just before ovulation, the primary oocytes completes mitosis l, making a secondary oocytes. The other product is smaller, it is called the polar body. The secondary oocytes and first polar body are both haploid.
Stage 5:
Primary follicles develope into secondary follicles, which are called Graafian follicles when mature. These migrate to the surface of the ovary where they burst and release the secondary picture during ovulation. Each month several primary follicles start to develop but normally only one mature into a fully developed Graafian follicle
Stage 6:
The secondary oocytes begins meiosis ll by stops at metaphase ll unless fertilisation takes place
Stage 7:
After fertilisation, meiosis ll is a completed, making an ovum containing most of the cytoplasm. The other product of meiosis ll is the second polar body.
Stage 8:
After ovulation the Graafian follicle become the Corpus Luteum (yellow body) If fertilisation occurs it produces hormones, otherwise it regresses.
How long must the sperm spend inside the female body before fertilisation
7 hours
What is capacitation?
Process that must occur in the sperm before it’s able to fertilised the oocyte. This involves the changing in membrane covering the acrosome, a thin cap over the nucleus of the nucleus of the sperm. This process may take several hours
What does the enzyme hyaluronidase?
Aids the sperm in its burrowing through the follicle cells which surrounds the oocyte
What is the acrosome reaction
Triggered when the sperm reaches the jelly-like coating of the egg called the zona-pellucida. The membrane becomes weakened and the sperm is able to penetrate it. A fine needle like filament developing at the tip of the sperm penetrates the membrane.
Describe the process of penetration with the oocyte and sperm
- The second meiotic division of the oocyte occurs which forms the ovum
- The second polar body degenerates and the ovum becomes fertilised
- A fertilising membrane forms around the ovum which prevents other sperms form entering. The formation of the membrane is called the cortical reaction
- The sperm loses its tail and it’s head moves towards the nucleus of the ovum.
- The head swells and it’s chromesomes join with those of the ovum to form a diploid cell called a zygote
What is the jelly like coating of the ovum called?
Zona pellucida
Why is it essential that fertilisation occurs internally in humans?
-optimum temperature
-safe environment
-nourished by nutrients
-in fluid so gametes don’t dry out
What is implantation?
when an embryo burrows deep into the lining of the uterus, where it can then begin to grow
What is cleavage?
When cells divide repeatedly but without an increase in cytoplasm
What is a morula?
When the zygote reaches the uterus as a small ball of cells
What is a blastula?
When the zygote divides to form a hollow fluid
What is a blastocyst?
A week after conception, when the blastula makes contact with the lining of the uterus
What are trophoblast cells?
They digest uterine cells and obtain nourishment from them. The blastula uses these to burrow into the uterine lining.
What is the hormone HCG (human chorionic gonadotropin) ?
An embryo releases this hormone whilst developing, it prevents degeneration of the Corpus luteum during pregnancy and ensures the correct hormone balance.
What is HCG used for?
Pregnancy tests use this hormone to detect/determine pregnancy.
What is female infertility?
When there is a blockage in the fallopian tubes. This forms a barrier between the oocyte and the spermatazoa and prevents fertilisation occuring
What hormone ensures that women don’t miscarry?
HCG- it maintains nourishment to the Corpus luteum for the first 16 weeks of pregnancy
When are progesterone and oestrogen secreted?
When the placenta is formed, these hormones rise to high levels in the blood plasma.
What hormones are inhibited during pregnancy
FSH and LH- prevents the development and maturation of further follicles and a subsequent pregnancies from taking place
What does progesterone do?
Surprises the contraction of the uterine wall. When the levels of progesterone drop then the female will naturally go into labour
What does oestrogen do?
Stimulates the growth of the uterus to accommodate the growing foetus and also stimulates the growth and development of the mammary glands during pregnancy
What does amniotic fluid do?
Surrounds the developing foetus to protect it by acting as a shock absorbed during development
When does oestrogen levels increase?
Just before birth and progesterone decreases and this allows uterine walls to contract
What is the function of oxytocin?
It is secreted by the posterior gland and stimulates contraction of the uterine wall which stimulates the secretion of oxytocin. This process is called positive feedback
What is prolactin?
Released by the anterior lobe of the pituitary gland during and after birth which stimulates the production of milk by the mammary gland
What is the menstrual cycle?
Each month, a follicle is stimulated to develope into an oocyte
