Sexual reproduction in humans Flashcards
What is the function of the ovaries?
Female sex organ that produces gametes. Secretes oestrogen and progesterone
What is the myometrium?
Muscle layer of uterus
What is the function of the cervix?
Neck of the uterus. Muscular ring that closes entrance to the uterus
What is the function of the fallopian tubes/oviducts?
Connect ovaries to uterus. Has ciliated epithelial cells lining it to waft the oocyte to the uterus
What is the function of the endometrium?
Innermost layer of the uterus. Embryo planted here. If not then shed layer
What is the function of the urethra in females?
Connect to bladder, allows urine passage
What is the function of the vagina?
Muscular tube that leads to outside of the body. Where the penis is inserted
What is the function of the seminal vesicle?
Glands secrete a mucus into vas deferens which contains nutrients for sperm
What is the function of the vas deferens?
Tube that takes sperm from testes to urethra during ejaculation
What is the function of the prostate gland?
Gland found at the base of bladder that secretes an alkaline solution which neutralises urine and aids sperm mobility
What is the function of the urethra in males?
Tube that connects bladder to outside. Urine and semen out.
What is the function of the epididymis?
Sperm collect and mature here
What is the function of the seminiferous tubules?
Tubes found in testes, site of sperm production
What is the function of the testes?
Produce male gametes (spermatozoa)
What is the function of the scrotum?
External sack that holds the testes outside of the body. Optimum sperm production temp is 35 degrees
What is the function of the penis?
Organ used to pass semen into reproductive system
What is the name of the process of how sperm are produced?
Spermatogenesis
How many stages are there in spermatogenesis?
6
What are the initial cells in spermatogenesis called?
Germinal epithelial cells
What do germinal epithelial cells divide into and by which process do they divide in spermatogenesis?
Divide by mitosis into spermatogonium
What do spermatogonium grow into?
Primary spermatocyte
What does a primary spermatocyte divide into and by which process does it divide?
Divides by meiosis 1 into two secondary spermatocytes
What do the two secondary spermatocytes divide into and by which process do they divide?
Divide by meiosis 2 into four spermatids
What do the four spermatids mature into?
4 spermatozoa
What is the function of Sertoli cells?
Secrete a fluid which nourishes the spermatids and protects them from the male immune system
What is the process of the development of the egg called?
Oogenesis
What happens alongside meiotic events in oogenesis?
Follicle development in the ovary
What are the initial cells in oogenesis called?
Germinal epithelial cells
What happens before being born in oogenesis?
Oogonia divide by mitosis and grow to form primary oocytes. Primary oocytes start meiosis 1 but stop at prophase 1.
Germinal epithelial cells divide to form the follicle cells that surround the primary oocyte to produce the primary follicles.
What happens at puberty in oogenesis?
Hormones stimulate one primary follicle to mature into a Graafian follicle. Primary oocyte completes meiosis 1 to become a secondary oocyte and a polar body. Secondary oocyte begins meiosis 2 but stops in metaphase two. Secondary oocyte released from Graafian follicle into ovary.
What happens at fertilisation during oogenesis?
If fertilised then secondary oocyte completes meiosis 2 to form an ovum and a second polar body
What is the zona pellucida?
A clear carbohydrate layer that surrounds the cell membrane of the secondary oocyte
What is the corona radiata?
A protective layer which surrounds the zona pellucida and the secondary oocyte
What is the antrum?
Section of an ovarian follicle which is filled with follicular fluid
When does oogenesis stop occurring?
Menopause
When does spermatogenesis stop occurring?
Death
Where is the precise site of production for oocytes?
Follicle in ovary
Where is the precise site of production for sperm?
Seminiferous tubules in testes
What is the first 14 days of the menstrual cycle called?
Follicular phase
What is the last 14 days of the menstrual cycle called?
Luteal phase
When does the menstrual cycle start?
From the onset of bleeding
What is the function of LH?
Ovulation
What is happening in the follicular phase of the menstrual cycle?
Anterior pituary gland secretes FSH causing follicle cells surrounding a primary oocyte to divide
Developing follicle cells secrete oestrogen which stimulates growth and increases blood supply of endometrium
FSH inhibited by oestrogen
Increasing LH has positive impact on FSH and it’s levels begin to increase again
Developing follicle becomes a Graafian follicle and LH peaks causing ovulation
What is happening in the luteal/secretory phase of the menstrual cycle?
Remaining follicle cells develop into corpus luteum which secretes oestrogen and lots of progesterone which maintains the endometrium
High progesterone and oestrogen levels inhibit LH and FSH
Causes corpus luteum to shrivel
Progesterone and oestrogen levels fall and endometrium is shed
FSH no longer inhibited and cycle begins again
What is the function of FSH?
Follicular development
What is the function of progesterone?
Maintain endometrium and inhibit LH and FSH
What is the function of oestrogen?
Increase blood flow to endometrium and stimulate growth. Inhibit FSH
Where are FSH and LH secreted from?
Anterior pituary gland
Where are oestrogen and progesterone secreted from?
Ovaries
Where does fertilisation take place?
Fallopian tube/oviduct
What is capacitation?
Caused by enzymes in nucleus. Removal of glycoproteins from sperm outer layer. Removal of cholesterol which weakens cell membrane, and makes it more permeable to calcium ions which increase tail activity and start acrosome reaction
What is the order of the sperms journey through the female reproductive tract?
Vagina –> cervix –> uterus –> oviduct/fallopian tube –> secondary oocyte
What is the acrosome reaction?
On contact with zona pellucida, the acrosome membrane ruptures and releases protease that hydrolyses the ZP
What happens if the sperm fuses with secondary oocyte?
Complete meiosis 2 and produces the ovum and second polar body
What is the function of the cortical reaction?
Produce a fertilisation membrane and prevents polyspermy
What is the cortical reaction?
Entry of sperm causes calcium ions to be released from SER of ovum. Cortical granules in ovum release enzymes that change structure of zona pellucida and prevent further sperm entry by producing a fertilisation membrane
How is the placenta adapted for exchange of substances?
Counter-current flow.
Maximise conc gradient between mother and foetus
Short diffusion pathway, moist, permeable
What cannot cross from mother to foetus through the placenta and why?
White blood cells - protect from mothers immune system
Blood borne pathogens to prevent illness
Why may pre-eclampsia (high blood pressure) cause medical problems for the mother and foetus?
High blood pressure could damage blood vessels and lead to bleeding. Would also allow WBCs from mother which would attack foetus
What is the function of the amniotic sac around the foetus?
Contains a fluid which maintains temp and provides lubrication
What happens to the cervix during labour?
Dilates
What is passed between the mother and foetus?
O2, CO2, glucose and urea
What cells surround the Graafian follicle?
Follicle cells/granulosa cells
What cells protect and nourish sperm cells?
Sertoli cells
What are the cells in the testes called which secrete testosterone?
Leydig cells
