human reproduction Flashcards
1
Q
define spermatogenesis
A
formation of sperm in the testes
2
Q
define oogenesis
A
formation of ova in the ovaries
3
Q
what is the role of sertoli cells?
A
cells which secrete a fluid which nourishes the spermatids and protects them from the immune system of the male
- they also provide oxygen and remove waste products
4
Q
what is the role of the interstitial cells / cells of Leydig?
A
cells which secrete testosterone which stimulates spermatogenesis and cause male secondary sexual characteristics to develop
5
Q
what is the function of the testes?
A
- there are 2 of these
- contain the seminiferous tubules and epididymis
6
Q
what is the function of the scrotum?
A
an external sac which protects the testes and keep them at normal body temperature (37C)
7
Q
what is the function of the penis?
A
intromittent organ that introduces sperm to the female uterus
8
Q
what is the function of the seminiferious tubules?
A
produce spermatazoa
9
Q
what is the function of the epididymus?
A
spermatazoa mature here and are stored before release
10
Q
what is the function of the vas defernes?
A
sperm pass along here from the epididymus to the urethra during ejaculation
11
Q
what is the function of the seminal vesicles?
A
produces a mucus secretion to help sperm motility
12
Q
what is the function of the prostrate gland?
A
produces an alkaline secretion that neutralises the urine and aids sperm motility
13
Q
what is the function of the urethra?
A
passageway between the bladder and external part of the body
14
Q
what is the function of the ureter?
A
connect the kidneys to the bladder
15
Q
what is the function of the ovary?
A
- two of these
- mitosis and meiosis I and II take places here to produce primary and secondary oocytes
- FSH and LH control the development and release of a secondary oocyte
16
Q
what is the function of the fallopian tube?
A
- ova pass through here to reach the uterus
- lined with ciliated epithelial cells
- fertilisation takes place here
17
Q
what is the function of the uterus?
A
- known as the womb
- has muscular walls (myometrium) and is lined by the endometrium
- oxytocin has a positive feedback effect here during birth
18
Q
what is the function of the endometrium?
A
- mucus membrane well supplied with blood
- embryo implants itself here during pregnancy
- it is shed during menstruation
- maintained by progesterone and oestrogen during the menstrual cycle
19
Q
what is the function of the cervix?
A
ring of muscle and connective tissue that is the entrance to the uterus
20
Q
what is the function of the vagina?
A
provides a passageway for blood and mucosal tissue from the uterus during a woman’s menstrual cycle
- receives the penis during sexual intercourse
- provides passageway for childbirth
21
Q
define gametogensis
A
production of gametes
22
Q
where does gametogenesis occur?
A
occurs in special paired glands called the gonads
23
Q
why do the germinal epithelium cells undergo mitosis and meiosis?
A
to produce genetically different haploid gametes
24
Q
- where are sperm made?
- what are sperm made from?
- what hormones are required for sperm development?
A
- sperm are made within the seminiferous tubules of the testes
- sperm cells are made from germinal epithelial cells
- hormones FSH and testosterone are required for sperm development
25
summarise spermatogenesis
- spermatozoa are produced in the seminiferous tubules of the testes by spermatogenesis
- spermatogonia divide many times to produce primary spermatocyte
- these undergo meiosis and the products of the first meiotic division are haploid secondary spermatocyte
- these undergo the second half of the meiotic division producing spermatids which differentiate and mature into spermatozoa
- spermatozoa are protected and nourished by the Sertoli cells
26
what is the function of the head in sperm cells?
contains a haploid nucleus and is covered at the end by a lysosyme called the acrosome which contains enzymes used in fertilisation
27
what is the function of the mid-piece in sperm cells?
packed with mitochondria which provide ATP for movement
28
what is the function of the tail in sperm cells?
the tail, or flagellum, makes lashing movements that move the sperm and allow motility
29
why are mitosis and meiosis important in spermatazoa production?
mitosis: produces large number of primary spermatocytes. this leads to large numbers of spermatocytes increasing the risk of fertilisation
meiosis: produces haploid spermatazoa and leads to genetic variation
29
summarise the process of oogenesis
PRE-BIRTH:
- germinal epithelial cells (2n) divide by mitosis to form oogonia (2n)
- oogonia undergo mitosis to form primary oocytes (2n)
- these undergo meiosis I but stop at prophase I
- this primary oocyte would be contained within a primary follice
AFTER PUBERTY:
- the primary oocyte completes meiosis I to form a secondary oocyte (n)
- this undergoes meiosis II but stops at metaphase II
- the primary follicle develops into a Graafian follicle containing the secondary oocyte
FERTILISATION:
secondary oocyte completes meiosis II to form an ovum
30
describe the structure of a secondary oocyte after ovulation
- a clear glycoprotein layer called the zona pellucida surrounds the cell membrane of the secondary oocyte
- the chromosomes of the secondary oocyte are at metaphase II
- corona radiata cells surround the secondary oocyte and provide nutrients
31
describe the menstrual cycle
- in the absence of an implanted embryo, the endometrium is shed through menstruation
- this occurs monthly from the start of puberty to menopause
- the menstrual cycle is a system of positive and negative feedback, operating between events involving the brain, the ovaries and the uterus
32
summarise the process of the menstrual cycle
- FSH secreted by anterior pituarity gland stimulates the maturation of a follicle, stimulating the production of follicle
- as a result, oestrogen (secreted by the developing follicle) increases in the blood which triggers the repair of the endometrium, inhibits FSH production and stimulates LH production
- a high level of LH, secreted by the anterior pituarity gland, initiates ovulation
- this cause the Graafian follicle to develop into a corpus luteum
- progesterone secreted by the corpus luteum causes further development of the endometrium prior to menstruation
- if implantation does not occur, falling FSH and LH levels cause the corpus luteum to degenerate, progesterone levels fall, the endometrium breaks down and is lost during menstruation
33
explain how oestrogen can be used as a contraceptive pill
- inhibits production of FSH so no new follicle develop
- without mature follicle, ovulation and fertilisation cannot take place
34
explain how progesterone can be used as a contraceptive pill
- prevents further production and secretion of LH
- progesterone increases level of mucus in cervix, blocks entry of sperm
- no ovulation so no fertilisation
35
IVF involves the maturation of a large number of follicles which can then be retrieved from the ovary. Suggest the hormone that would be provided to patients and explain your answer.
- FSH
- responsible for primary follicle developing into Graafian follicles
36
describe the process of copulation
- arterioles entering the penis dilate and the venules leaving the penis constrict
- the build up of blood in the penis cause it to become erect
- the penis is inserted into the vagina
- movements of the penis result in the ejaculation of sperm into the vagina
- the force of ejaculation is sufficient to propel some sperm through the cervix into the uterus, with the remainder being deposited at the top of the vagina
36
what are the 3 stages of fertilisation?
1. capacitation
2. acrosome reaction
3. cortical reaction
37
outline the process of capacitation
- sperm can only fertilise a secondary oocyte after capacitation which can take several hours
- this involves changes in the cell membrane covering the acrosome where cholesterol and glycoproteins are removed
- this increases the permeability of the acrosome membrane to calcium ions and improves the sperm's motility
38
outline the process of the acrosome reaction
- spermatozoa push their way through the cells of the corona radiata
- on contact with the zona pellucida, the acrosome membrane ruptures and releases hydrolase enzymes which digest a path through the zona pellucida
- the membranes of the sperm and secondary oocyte fuse and the genetic material of the sperm (haploid nucleus) enters the secondary oocyte
39
outline the process of the cortical reaction
- once a sperm has successfully penetrated the secondary oocyte, the oocyte's smooth endoplasmic reticulum releases calcium ions into the cytoplasm
- the arrival of the calcium ions causes cortical granules fuse with the cell membrane and release their contents to modify the zona pellucida
- the zona pellucida hardens to form the fertilisation membrane
- this prevents other sperm from being able to penetrate the egg (polyspermy)
40
what does the entry of the sperms genetic material trigger?
meiosis II
- to continue forming the ovum and a polar body
41
why is it important that a fertilisation membrane forms?
to ensure a diploid zygote forms
42
describe the process of implantation
- zygote undergoes repeated mitotic divisions, called cleavage, to form a ball of cells
- cleavage continues and by seven days the ball of cells becomes hollow and is called a blastocyst
- the blastocyst is moved into the uterus where it attaches and embeds into the endometrium - implantation
43
what is the amniotic fluid?
the embryo (later the foetus) develops and grows in the uterus enclose in the amnion - a membrane that is derived from the blastocyst
44
what are the roles of the amniotic fluid?
- maintains the foetal temperature
- acts as a shock absorber, protecting the foetus from injury outside the uterus
45
suggest 2 concerns the some people may have about the ethics of prenatal diagnosis
- selective abortion may become more common
- moral status of foetus/right to live
- may cause harm to foetus
- could result in false (positive/negative) results
46
what is the placenta?
forms between the tissues of the mother and the foetus and is connected to the foetus by the umbilical cord
47
what is the function of the umbilical vein and artery?
umbilical vein : carries blood containing oxygen and glucose TO the foetus
umbilical artery : carries deoxygenated blood containing carbon dioxide AWAY from the foetus
48
where are foetal capillaries found?
within chorionic villi which form the boundary between maternal and foetal blood
49
describe the exchange of blood between the mother and foetus
- blood from maternal arterioles empties into an intervillous space
- there are no maternal capillaries between the maternal arteriole and maternal venule so there is one less layer of cells for diffusion to occur across which provides a shorter diffusion pathway for materials
- foetal capillaries bathe in this intervillous space for exchange of materials to occur
- blood containing waste materials will then return to maternal venules from the intervillous space
50
what are the roles of the placenta?
- exchange of materials takes place across a thin barrier which separates maternal and foetal blood
- provides protection from the immune system of the mother
- protects the foetus from the differences in maternal and foetal blood pressures as the mothers blood pressure would be too high for the foetus
- allows the passage of maternal antibodies into the foetus to provide short term immunity
51
what materials go into foetal blood?
glucose
oxygen
amino acids
salts
52
what material go out of foetal blood?
carbon dioxide
nitrogenous waste
53
54
what secretes hCG?
when is hCG secreted?
what is the function of hCG?
- developing embryo secretes hCG
- before and following implantation
- maintains corpus luteum for the first 16 weeks of pregnancy
55
what secretes progesterone and oestrogen and why?
the placenta secretes progesterone and oestrogen which rise to high levels in the blood plasma
- these hormones suppress the secretion of FSH and LH
56
why are FSH and LH suppressed?
FSH : so no more follicles mature
LH : so no ovulation takes place
57
what is the role of progesterone during pregnancy?
suppresses the uterine walls ability to contract and maintains the endometrium
58
what is the role of oestrogen during pregnancy?
stimulates the growth of the uterus to accommodate the growing foetus and stimulates the growth and development of the mammary glands
59
describe oxytocin
- secreted by posterior pituarity gland
- stimulates contraction of the myometrium
- these contractions stimulate the secretion of more oxytocin (example of positive feedback)
- as the levels of oxytocin increase, the contractions become stronger and more frequent
60
describe prolactin
- released from anterior lobe of the pituarity gland during and after birth
- stimulates the production of milk by the mammary glands
61
what causes the uterine wall to contract?
increase in oestrogen levels and decrease in progesterone levels
