11.08 Testicular Function Flashcards Preview

11. Reproduction > 11.08 Testicular Function > Flashcards

Flashcards in 11.08 Testicular Function Deck (30):
1

How does the reproductive system support gametes?

  • Produces gametes
  • Stores gametes
  • Nourishes gametes
  • Transports gametes

2

What are the 2 distinct functions of the reproduction organs?

  1. Gametogenesis (Spermatogenesis and Oogenesis)

  2. Secretion of hormones

3

What is spermatogenisis?

What is oogenesis?

Spermatogenesis is the production of mature Spermatozoa from sertoli cells in seminiferous tubules of the Testes 

 

Oogenesis is the production of Ova (eggs) in the Ovary

4

What are the three major hormones secreted by the reproductive organs?

 

What produces each hormone?

  1. Testosterone from the Leydig Cells in the interstitial Tissue
  2. Oestrogen and Progesterone from the theca and granulosa cells of the Follicle

 

5

Is testosterone solely present in men and oestrogen/progestrone solely in women?

No there is lots of overlap between these hormones between sexes

6

Is reproduction essential to whole body homeostasis?

No.

It is not necessary for the life of the individual but it is critical to the propagation of the species

7

What are the [2] reproductive functions of the male system?

  1. Spermatogenesis
  2. Delivery of sperm to the female

8

The female reproductive system is much more complex.

 

What are the [6] major reproductive functions of the female system

  1. Oogenesis
  2. Reception of sperm (at the right time)
  3. Fertilization
  4. Gestation
  5. Parturition
  6. Lactation

9

Fill in the Blanks:

  • At the end of mitosis, the developing sperm is called a _________
  • Human gametes have ___ chromosomes

  • At the end of mitosis, the developing sperm is called a Spermatocyte
  • Human gametes have 23 chromosomes

10

Define gametogenesis

The process in which precursor cells (diploid) undergo meiosis to form gametes - the reproductie cells (haploid cells) .

11

Germs cells exist in the embryonic gonad (present in the embryo during foetal birth). 

What are the types of divisions that happen to these germ cells in gametogenesis?

  1. Firstly, mitotic divisions increase the number of germ cells present
  2. Meiosis produces

    • A Primary gamete

    • A secondary gamete

    • A mature haploid gamete

12

Describe the timing of gametogenesis in males vs. females

 

Describe what signals the beginning of this process in both sexes

  • In males gametogenesis begins in puberty
  • In females gametogenesis begins as a foetus but is arrested in the first meiotic division until puberty)

 

During puberty there is a GnRH pulsatile surge that causes either the release of testosterone for men or oestrogen/progesterone in women to allow gametogenesis to begin/resume. 

13

What is the major site of spermatogenesis?

Within the very coiled structured seminiferous tubules of the testes.

 

The spermatogonium (earliest precursor cells) are arranged on the outer most later of the tubule (ie. away from the lumen) and as they mature they move up towards the lumen and slough off and through the tubule as a mature sperm.

14

What is the first step of spermatogenesis?

The spermatogonium divides by mitosis into 2 identical daugher cells:

  • One daughter cell remains on the outer surface to maintain germline
  • The other daughter cell undergoes further mitotic proliferation (to produce primary spermatocytes) and moves towards the lumen 

15

Describe the process of spermatogenesis:

  1. Spermatogonium undergos mitosis into 2 identical daughter cells.
  2. One of the daugther cells (called spermatogonia) will undergo mitosis (proliferate) to form primary spermatocytes
  3. Primary spermatocytes undergo the first meiosis (this is where the diploid cell becomes haploid) to form secondary spermatocytes
  4. Secondary spermatocytes undergo a second meiosis to form a spermatid
  5. The spermatid undergoes packaging and maturation to form the mature spermatozoa
  6. Spermatozoa slough off the surface of the tubule into the lumen.

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16

From what cell is the major source of testosterone in males?

From Leydig cells (interstitial cells)
 

17

Describe steroid hormone synthesis (in relation to the sex hormones)

Cholesterol backbone is modified sequentially in the adrenal glands to give Testosterone which is convered by aromatase to oestrogen. 

 

This process of steroid hormone production also occurs in the gonads. 

 

 

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18

Describe the regulation of the sex hormones 

(ie. the Hypothalamic-Pituitary-Gonad Axis)

  • Gonadotrophin Releasing hormone from the hypothalamus
  • Acts on the anterior pituitary cells to release both Follicle stimulating hormone (FSH) and leutanizing hormone (LH)
  • These travel in the circulation to the gonads and interact with receptors

 

LH = sex hormone production

FSH = gamete production

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19

How does the CNS impact on the reproduction hormone axis

Higher centres like stress and other disease states impact on cycles (particularly females) usually to reduce the GnRH secretion.

20

In males, which cell specifically does LH and FSH act on?

LH acts on leydig cells to cause the release of testosterone.

 

FSH acts on Sertoli cells to stimulate spermatogenesis

21

What are the major male reproductive structures?

Draw the anatomy

  • Testes contains the seminiferous tubules and is the site of spermatogenesis
  • The epididymis is the site of sperm maturation
  • Sperm travels via the vas deferns through several accessory glands: seminal vesicle, prostate gland and bulbourethral gland
  • The vas deferens joins the urethra from the bladder for a common outlet tract via the penis

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22

What is important about the vasculature of the penis?

Penis has a complex vasculature with high anastomoses to enable it to be erect and have effective delivery of sperm into the vagina. 

  • Corpus spongiosum

  • Corpora cavernosa

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23

Describe the seminiferous tubule

Seminiferous tubules

  • Sertoli cells surround and support spermatogenesis

 

Interstitial tissues support spermatogenesis

  • Leydig cells􏰀 produce testosterone and some nutrients for spermatogenesis
  • Capillaries deliver nutrients and remove wastes

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24

Label the following diagram

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25

What is inhibin?

Another hormone secreted by the gonads (sertoli cells in males and granulosa cells in females) that regulates the secretion of FSH (and LH: testosterone)

 

 

26

After the GnRH surge after puberty, testosterone secretion becomes continuous in males.

 

What are the consequences of testosterone production?

  • Before Birth
  • In reproductive organs
  • To reproduction itself
  • Secondary characteristics
  • Non-reproductive

Before Birth

  • Masculinises reproductive tract and external genitialia
  • Promotes descent of testes into scrotum

Sex‐specific tissues

  • Promotes growth and maturation of reproductive system
  • Spermatogenesis

Other reproductive effects

  • Sex drive;
  • Control of Gonadotropin secretion

Secondary sexual effects

  • hair growth (beard, chest, pubic)
  • voice to deepen
  • muscle growth and body configuration

Non-reproductive Actions

  • protein anabolic effects, bone growth, closure of epiphyses, sebaceous gland secretions

27

Semen is a complex fluid with all of the compenents that make it up coming from different structures and all of the essential to the function. 

 

What are the components of sperm? [8] the source and the function

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28

Describe the signaling process that occurs after FSH binds to the receptors present in the testes

  • Binding to receptors on sertoli cells
  • second messenger actions
  • to cause the production of cell products
    • Stimulation of spermatogenesis

    • Production of Inhibin that negatively feedsback on FSH release

    • Procuction of Androgen-binding protein (ABP) critical to binding testosterone in the testes so it can have its actions. 

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29

Describe the signalling processes that occur once LH binds to the receptors in the testes

  • Binding to receptors on Leydig Cells of the interstitium
  • Causes the production and release of testosterone
    • Testosterone then acts on the sertoli cells to nurture and support the process (must bind to androgen-binding protein
    • Has secondary body effects 

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30

Describe the controversial concept of andropause

Males have a huge life cycle of reproductive capacity. Remaining reproductively active throughout life after puberty.

Andropause only affects around 50% of men over 50 yrs old and the lower levels of testosterone impact some men’s lives