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Module 203 Reproduction & endocrinology > T2 L9 & 10 Short but happy life of a sperm > Flashcards

T2 L9 & 10 Short but happy life of a sperm Flashcards

1
Q

What are the functions of the testis?

A

Production of spermatozoa

Production of hormones

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2
Q

What are the 2 compartments of the testes?

A

Seminiferous tubules

Vascularised stroma

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3
Q

Where does spermatogenesis occur?

A

In the seminiferous tubules

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4
Q

What is the structure of the seminiferous tubules?

A

Surrounded by myoid cells then a layer of basement membrane
Sertoli cells and spermatogenic cells within the tubules
Physiological barrier formed by gab and tight junction complexes between Sertoli cells

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5
Q

What is the purpose of the physiological barrier formed between Sertoli cells?

A

Creates basal compartment containing spermatogonia whilst spermatocytes, spermatids and spermatozoa are in a separate adluminal compartment

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6
Q

Where are Leydig cells?

A

In the vascularised stroma

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7
Q

What are the most important hormones in maintaining reproductive and sexual function?

A

Androgens

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8
Q

What is testosterone synthesised from?

A

Acetate and cholesterol by Leydig cells

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9
Q

How much testosterone is secreted daily?

A

4-10mg

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10
Q

What is testosterone converted to in Sertoli cells?

A

Dihydrotestosterone

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11
Q

What stimulates Leydig cells to produce androgens?

A

LH

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12
Q

What stimulates Sertoli cells?

A

FSH

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13
Q

What are the 3 stages of spermatogenesis?

A

1) Mitotic proliferation to produce lots of cells
2) Meiotic division to generate genetic diversity
3) Cell modelling to package chromosomes for delivery to oocyte

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14
Q

Describe the first stage of spermatogenesis

A

Germ cells of immature testis are activated at puberty undergo rounds of mitosis in basal compartment of tubule
From this self-regenerating population, a group of cells called A1 spermatogonia emerge
After last round of division, clone divides to form resting primary spermatocytes
Cytoplasmic division isn’t completed so all primary spermatocytes from division of spermatogonium are linked by cytoplasmic bridges

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15
Q

Describe the second stage of spermatogenesis

A

Resting primary spermatocytes push through Sertoli cell junctions into adluminal compartment
Enter meiotic prophase
Paired homologous chromosomes form contacts at pachytene, break and swap segments and re-join
First division ends with separation of homologous chromosomes to opposite ends of meiotic spindle, cytoplasm divides to form short-lived secondary spermatocytes
Quickly divide to form haploid spermatids

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16
Q

Describe the third stage of spermatogenesis

A 
Cytoplasmic remodelling of spermatid
Tail for forward propulsion
Midpiece with mitochondria for energy 
Nucleus with package chromosomes
Cap region forms for sperm-oocyte fusion
Acrosome forms to penetrate oocyte
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17
Q

How many spermatozoa are produced per second?

A

300-600 per gram of testis per second

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18
Q

How long does spermatogenesis take?

A

64 days

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19
Q

Describe the spermatogenic cycle

A

Once the generation of sperm from a single spermatogonium has started, new stem cells at the same location don’t start generation of clones again for a few days

20
Q

What would happen if all spermatogonia were activated on 11th birthday?

A

It would only produce mature spermatozoa every 16 days resulting in episodic fertility

21
Q

Describe the later events in maturation of sperm

A

Spermatozoa wash into rete through vasa efferentia
Into the epididymis where fluid is absorbed and sperm is concentration
In the rete they can twitch
In the cauda epididymis they can swim

22
Q

What are the final stages of maturation dependent on?

A

Androgen stimulation

23
Q

What is semen?

A

Spermatozoa mixed with secretions from seminiferous tubules, epididymis etc.

24
Q

What are the cellular components of semen?

A

Spermatozoa
Epithelial cells from tract
Spermatogenic cells
Leucocytes - risk of HIV etc.

25
Q

What are the fluid components of semen?

A

Nutrition (fructose, sorbitol)
Buffer
Antioxidants

26
Q

Why is a buffer needed in semen?

A

To protect against vaginal acidity

27
Q

Give examples of antioxidants in semen

A

Ascorbic acid

Hypotaurine

28
Q

What effect does oestrogen have on cervical mucus?

A

Causes secretion of watery mucus

29
Q

What effect does progesterone have on cervical mucus?

A

Inhibits secretory activity

30
Q

What is the role of the endocervix for sperm?

A

Receptive to sperm at time of ovulation, interference at other times
Protection from hostile vagina and being phagocytosed
Supplementation of energy requirements
Sperm selection by differential motility and morphology
Short term reservoir with endocervical cysts
Initiation capacitation

31
Q

What is capacitation?

A

Stripping of glycoprotein from sperm surface which accumulates in epididymis
Causes hyperactive motility
Makes sperm responsive to signals from oocyte

32
Q

What are the 3 properties of cervical mucus?

A

Consistency
Spinnbarkeit - elasticity, stickiness
Ferning - crystallisation on glass surface

33
Q

What ways can sperm be analysed?

A

Volume
Concentration and vitality
Motility
Morphology

34
Q

What can cause a low ejaculation volume?

A

Retrograde ejection

35
Q

What can cause a high ejaculation volume?

A

Abstinence or accessory gland inflammation

36
Q

Define sperm concentration or density

A

The number of sperm per ml in the total ejaculate

37
Q

What is the normal sperm concentration?

A

> 15 million per ml

38
Q

Describe motility

A

Percentage of progressively motile sperm in ejaculate

39
Q

What does progressively motile mean?

A

They go somewhere rather than swimming round in circles

40
Q

Wha are the visual types of sperm?

A 
Normal
Large head
Small head
Double tail
Double head
Tapered head
Coiled tail
Immature form
Shapeless head
Cytoplasmic droplets
Abnormal midpiece
41
Q

What is normozoospermia?

A

Normal values of sperm

42
Q

What is oligozoospermia?

A

Low concentration of sperm

43
Q

What is asthenozoospermia?

A

Too little motility

44
Q

What is teratozoospermia?

A

Too many abnormals

45
Q

What is azoospermia?

A

No spermatozoa

46
Q

What is aspermia?

A

No ejaculate

Module 203 Reproduction & endocrinology (52 decks)

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