Week 7.0 - Coitis and fertilisation Flashcards Preview

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Flashcards in Week 7.0 - Coitis and fertilisation Deck (77):
1

How long does it take for spermatogonia to mature into spermatozoa?

-upto 74 days (50 in testis 12-24 in epididymis)

2

When does spermatogenesis begin/end?

-From puberty until death

3

How many of the sperm produced per day become viable sperm?

-50%

4

Does production of sperm stay the same throughout life?

-Decreases in quantity and quality with age

5

Which hormone acts on the leydig cells? What is the result of this?

-LH
-Production of testosterone

6

Which hormone acts on the sertoli cells? What is the result of this?

-FSH
-Antigen binding protein production leading to the concentration of testosterone in luminal fluid enabling spermatogenesis

7

If the pituitary gland is removed, how is spermatogenesis stimulated?

-FSH and testosterone

8

What is the function of oestrogen in the testis?

-Increase sperm viability

9

What is nuclear condensation and when does it happen?

-Extrusion of the cytoplasm and condensation of the nucleus from spermatid to spermatozoon

10

What does the acrosome contain? Why?

-Golgi apparatus and hydrolytic enzymes to enable sperm to penetrate ovum

11

Identify the main feature of the midpiece of a spermatozoon
Why is this needed?

-Mitochondria packed around either side
-Motility is a highly energy dependant process

12

What is the tail of a sperm made from?

-Flagellum produced by microtubules

13

What signals for the cytoplasm and organelles to be stripped from the permatid?

-Testosterone

14

What is different between the mature spermatozoa in the seminiferous tubules and the mature spermatozoa in the epididymis?

-Lack motility in the seminiferous tubules

15

What is spermiation?

-Release of spermatozoa from sertoli cells into seminiferous lumen

16

How are spermatozoa transported from seminiferous lumen to epididymis?

-Testicular fluid (produced by sertoli cells) and peristaltic contraction

17

How long can mature spermatozoa stay in the epididymis?

-Several months, eventually phagocytosed

18

How do the spermatozoa get into ductus deferens?

-Upon sexual arousal the epididymal wall contracts and expels the sperm into the ductus deferens

19

What are the phases of coitus?

-Excitement phase
-Plateau phase
-Orgasmic phase
-Resolution phase

20

What is the refractory period in males?

-After ejaculation it is not possible to ejaculate again upon further stimulation

21

Describe the excitement phase of the male sexual response

-Sensory and psychological stimulation
-Inhibition of sympathetic outflow (thoracolumbar)
-Activation of parasympathetic outflow (sacral)
-Ach-> M3 on endothelial cells of penile bvs -> increased Ca-> activation of eNOS -> NO production
-Arterial vasodilation in corpora cavernosa
-Increased penile blood flow
-Penile filling (full of blood but not erect)
-Penile tumescence (erection)

22

What happens to the testes and scrotum upon sexual arousal?

-Testes elevate and engorge and scrotal skin thickens and tenses

23

Describe the plateau phase of male sexual response

-Activation of sacrospinous reflex
-Contraction of ishiocavernosus -> compresses crus of penis and impedes venous return -> venous engorgement
-Rise in intracavernosus pressure higher than systolic pressure -> decreased arterial inflow
-Stimulation of secretion from accessory glands
-Loss of erection unlikely

24

Which accessory glands are stimulated in the plateau phase of male sexual response?

-Cowpers glands
-Littre's glands

25

What are the two stages of orgasmic phase in male sexual arousal?

-Emission
-Ejactulation

26

Describe the emission stage of orgasmic phase in male sexual response

-Stimulation of sympathetic reflex
-Contraction of smooth muscle in ductus deferens, seminal vesicle and prostate
-Internal and external urethra contracts
-Semen becomes pooled in urethral bulb

27

Describe the ejaculation stage of orgasmic phase of male sexual response

-Sympathetic spinal reflex with cortical control
-Further contraction of glands and ducts and sphincters
-Filling of urethra stimulates pudendal nerve-> contractions of the genital organs, ischiocavernosus and bulbocavernosus -> expulsion of semen

28

Describe the resolution phase of the male sexual response

-Activation of sympathetic outflow
-Contraction of arteriolar smooth muscle in corpora cavernosa
-Increased venous return
-Detumescence and flaccidity
-Testes descend and scrotum thins and relaxes
-Refractory period entered

29

Describe the excitement phase of the female sexual response

-Sensory and psychological stimulation
-Activation of parasympathertic outflow; inhibition of sympathetic outflow
-Vasocongestion causes vaginal lubrication to begin
-Clitoris becomes engorged with blood
-Uterus elevates, inner 2/3 of vagina lengthens and expands
-Increased muscle tone, HR and BP

30

Describe the plateau phase of female sexual response

-Further increase in muscle tone, HR and BP
-Labia minora deepen in colour
-Clitoris withdraws under its hood
-Barthlin glands secretions lubticates vestibule for entry of penis
-Orgasmic platform forms in lower 1/3 of vagina, upper 2/3 fully distended and uterus is fully elevated

31

Describe the orgasmic phase of the female sexual response

-Orgasmic platform contracts rhythmically 3-15 times
-Uterus contracts, anal sphincter contracts
-Clitoris remains retracted under its hood
-No refractory period - multiple orgasms possible

32

In which direction does the uterus contract during a female orgasm?

-From fundus down to cervix

33

Describe the resolution phase of the female sexual response

-Clitoris descends and engorgement subsides
-Labia returned to unaroused colour and size
-Uterus descends
-Vagina shortens and narrows back to unaroused state

34

What happens to the breasts during female sexual response?

-Breasts increase in size
-Nipples become erect
-Areola increases in size
-Sex flush

35

What is 'the G spot'?

-Area of erotic sensitivity located on the anterior wall of the vagina which can stimulate female ejaculation in some women
-Tissue similar to prostate

36

What happens to the female sexual response cycle with age?

-Reduced desire
-Reduced vasocongestion-> reduced vaginal lubrication
-Vaginal and urethral tissue loose elasticity
-Length and width of vagina decrease with reduced expansile capacity
-Number of orgasmic contractions reduced

37

What is the most common problem in sexual dysfunction? How can it manifest?

-Desire
-Hypoactive, aversion, hyperactive nymphomania/satyriasis

38

What is Kluver Bucci syndrome?

-Bilateral medial temporal lobe lesion causing hyperphagia, hypersexuality, hyperorality, visual agnosia and docility

39

What is arousal sexual dysfunction in females?

-Persistent, recurrent inability to attain or maintain lubrication-swelling response

40

What is arousal sexual dysfunction in males? Give some causes

-Impotence
-Psychological, tissue damage, vascular damage, drugs (alcohol/anti-hypertensives)

41

How does viagra work?

-Inhibits cGMP breakdown causing increased Ca and Increased NO production

42

How much semen is produced in one ejaculation?

-2-4 ml

43

How many sperm in one ejaculation?

-20-200x10^6/ml

44

How many sperm are viable per ejaculation?

-60% (at least 30% abnormal)

45

What is the definition of abnormal low sperm count?

-less than 20 million/ml

46

Describe the glandular secretions from the seminal vesicles

-Make up 60% of ejaculate
-Alkaline fluid to neutralise urethra, fructose for ATP production, prostaglandins and clotting factors (semenogelin)

47

Why does semen contains prostaglandins?

-Increases sperm motility and female genital smooth muscle contraction

48

Why does semen contain clotting factors?

-Liquefaction of semen in 1 hour

49

Describe the glandular secretions from the prostate

-25% of ejaculate
-Milkym slightly acidic secretion containing proteolytic enzymes (PSA/pepsinogen) and citric acid

50

Why do prostate secretions contain proteolytic enzymes?

-Activate clotting factors

51

Describe the glandular secretions from the bulbourethral glands

-5% of ejaculate
-Alkaline fluid to neutralise distal urethra

52

Where is semen depositied?

-High in the vagina near external os

53

During the secretory phase of the uterine cycle, describe the mucus at the cervix
Why?

-Thick, sticky, acidic mucus plug to prevent bacterial inflow

54

What is the function of oxytocin in sperm transport?

-Stimulates uterine contraction to propel sperm

55

Describe cytoplasmic maturation in the oocyte

-Organelles become arranged around the periphery, lipid and protein synthesis occurs

56

How many sperm does it take for fertilisation?

-Out of 200-300 million sperm, ~300 reach the fertilisation site
-299+ sacrificed to disperse the zona pellucida -> 1 for fertilisation

57

How long can sperm survive in the female genital tract?

-upto 5 days

58

How long does the ovulated oocyte survive?

-6-24 hours before phagocytosis

59

When is the fertile period when sperm needs to be depositied?

-Upto 3 days prior to ovulation and on day of ovulation

60

How and how long does fertilised oocyte take to travel to uterus?

-3/4 days via peristalsis and cilia

61

What does the sperm need to penetrate on the oocyte for fertilisation?

-Corona radiata
-Zona pellucida

62

What is capacitation?

-The final stage of spermatozoa maturation which takes place in the female genital tract
-Cell membrane changes to allow fusion with oocyte surface by removal of protein coat of sperm, exposing the acrosomal enzymes
-Tail changes from beat to whip-like action

63

What is the acrosome reaction?

-When sperm pushes through granulosa cells of corona radiata it has intact acrosome
-Protein coat then binds to ZP3 proteins of zona pellucida triggering acrosome reaction
-Path digested through ZP and one sperm penetrates and fuses with oocyte forming zygote

64

Where abouts in meiosis II of the oocyte is it halted?

-Metaphase

65

Describe sperm-oolemma binding and fusion

The oocyte has two regions of its PM: that which directly overlies metaphase chromosomes and is devoid of microvilli and the rest is rich in microvilli protrusions. The sperm binds to the microvilli

66

What is the fast block to polyspermy?

-As soon as a sperm penetrates the zona pellucida there is an electrical change in the oocyte membrane -> Na channels open increasing the membrane potential to +25 mv. This causes a wave of depolarisation which starts at the site of sperm entry and propagates across the cytoplasm -> this prevents sperm from fusing

67

What is the slow block to polyspermy?

-Ca released from ER induces local exocytosis of cortical granules-> granules release enzymes to stimulate adjacent granules to undergo exocytosis
-Wave of exocytosis around the oocyte alters the zona pellucida in such a way that sperm can no longer penetrate

68

What is syngamy?

-Completion of meiosis II with extrusion of polar body
-Male and female pronuclei migrate towards each other and fuse to form diploid zygote

69

What is polyploidy?

-Embryos containing 3 or more pronuclei (polyspermy of failure of polar body extrusion

70

What is cleavage?

-A series of rapid mitotic divisions which increases zygote cell number but not size thus increasing the nucleus:cytoplasmic ratio

71

How do monozygotic twins occur as a result of cleavage?

-Totipotent cells become divided into 2 separate individual cell masses

72

How do you get non-identical twins?

-Two eggs ovulates, two eggs fertilised

73

What is compaction?

-At the 8 cell stage, blastomeres undergo compaction where cells become polarised and communicate by tight junctions

74

What is a morula?

-16 stage blastomere as embryo passes into uterus

75

What is hatching?

-Local digestion of zona pellucida by enzymes produced by trophoblast so it can begin implantation

76

Does the conceptus implant immediately after entered uterus?

-No, nourished in an intrauterine fluid for 2-3 days

77

Where are spermatozoa produced?

-Seminiferous tubules