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biology - component 2 > human reproduction > Flashcards

human reproduction Flashcards

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1
Q

define spermatogenesis

A

formation of sperm in the testes

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2
Q

define oogenesis

A

formation of ova in the ovaries

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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

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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

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5
Q

what is the function of the testes?

A
  • there are 2 of these
  • contain the seminiferous tubules and epididymis
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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)

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7
Q

what is the function of the penis?

A

intromittent organ that introduces sperm to the female uterus

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8
Q

what is the function of the seminiferious tubules?

A

produce spermatazoa

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9
Q

what is the function of the epididymus?

A

spermatazoa mature here and are stored before release

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10
Q

what is the function of the vas defernes?

A

sperm pass along here from the epididymus to the urethra during ejaculation

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11
Q

what is the function of the seminal vesicles?

A

produces a mucus secretion to help sperm motility

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12
Q

what is the function of the prostrate gland?

A

produces an alkaline secretion that neutralises the urine and aids sperm motility

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13
Q

what is the function of the urethra?

A

passageway between the bladder and external part of the body

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14
Q

what is the function of the ureter?

A

connect the kidneys to the bladder

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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
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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
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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
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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
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19
Q

what is the function of the cervix?

A

ring of muscle and connective tissue that is the entrance to the uterus

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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

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21
Q

define gametogensis

A

production of gametes

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22
Q

where does gametogenesis occur?

A

occurs in special paired glands called the gonads

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23
Q

why do the germinal epithelium cells undergo mitosis and meiosis?

A

to produce genetically different haploid gametes

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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
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25
Q

summarise spermatogenesis

A
  • 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
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26
Q

what is the function of the head in sperm cells?

A

contains a haploid nucleus and is covered at the end by a lysosyme called the acrosome which contains enzymes used in fertilisation

27
Q

what is the function of the mid-piece in sperm cells?

A

packed with mitochondria which provide ATP for movement

28
Q

what is the function of the tail in sperm cells?

A

the tail, or flagellum, makes lashing movements that move the sperm and allow motility

29
Q

why are mitosis and meiosis important in spermatazoa production?

A

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
Q

summarise the process of oogenesis

A

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
Q

describe the structure of a secondary oocyte after ovulation

A
  • 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
Q

describe the menstrual cycle

A
  • 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
Q

summarise the process of the menstrual cycle

A
  • 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
Q

explain how oestrogen can be used as a contraceptive pill

A
  • inhibits production of FSH so no new follicle develop
  • without mature follicle, ovulation and fertilisation cannot take place
34
Q

explain how progesterone can be used as a contraceptive pill

A
  • prevents further production and secretion of LH
  • progesterone increases level of mucus in cervix, blocks entry of sperm
  • no ovulation so no fertilisation
35
Q

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.

A
  • FSH
  • responsible for primary follicle developing into Graafian follicles
36
Q

describe the process of copulation

A
  • 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
Q

what are the 3 stages of fertilisation?

A
  1. capacitation
  2. acrosome reaction
  3. cortical reaction
37
Q

outline the process of capacitation

A
  • 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
Q

outline the process of the acrosome reaction

A
  • 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
Q

outline the process of the cortical reaction

A
  • 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
Q

what does the entry of the sperms genetic material trigger?

A

meiosis II
- to continue forming the ovum and a polar body

41
Q

why is it important that a fertilisation membrane forms?

A

to ensure a diploid zygote forms

42
Q

describe the process of implantation

A
  • 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
Q

what is the amniotic fluid?

A

the embryo (later the foetus) develops and grows in the uterus enclose in the amnion - a membrane that is derived from the blastocyst

44
Q

what are the roles of the amniotic fluid?

A
  • maintains the foetal temperature
  • acts as a shock absorber, protecting the foetus from injury outside the uterus
45
Q

suggest 2 concerns the some people may have about the ethics of prenatal diagnosis

A
  • 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
Q

what is the placenta?

A

forms between the tissues of the mother and the foetus and is connected to the foetus by the umbilical cord

47
Q

what is the function of the umbilical vein and artery?

A

umbilical vein : carries blood containing oxygen and glucose TO the foetus
umbilical artery : carries deoxygenated blood containing carbon dioxide AWAY from the foetus

48
Q

where are foetal capillaries found?

A

within chorionic villi which form the boundary between maternal and foetal blood

49
Q

describe the exchange of blood between the mother and foetus

A
  • 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
Q

what are the roles of the placenta?

A
  • 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
Q

what materials go into foetal blood?

A

glucose
oxygen
amino acids
salts

52
Q

what material go out of foetal blood?

A

carbon dioxide
nitrogenous waste

53
Q
A
54
Q

what secretes hCG?
when is hCG secreted?
what is the function of hCG?

A
  • developing embryo secretes hCG
  • before and following implantation
  • maintains corpus luteum for the first 16 weeks of pregnancy
55
Q

what secretes progesterone and oestrogen and why?

A

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
Q

why are FSH and LH suppressed?

A

FSH : so no more follicles mature
LH : so no ovulation takes place

57
Q

what is the role of progesterone during pregnancy?

A

suppresses the uterine walls ability to contract and maintains the endometrium

58
Q

what is the role of oestrogen during pregnancy?

A

stimulates the growth of the uterus to accommodate the growing foetus and stimulates the growth and development of the mammary glands

59
Q

describe oxytocin

A
  • 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
Q

describe prolactin

A
  • released from anterior lobe of the pituarity gland during and after birth
  • stimulates the production of milk by the mammary glands
61
Q

what causes the uterine wall to contract?

A

increase in oestrogen levels and decrease in progesterone levels

biology - component 2 (7 decks)

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