11.08 Testicular Function Flashcards
How does the reproductive system support gametes?
- Produces gametes
- Stores gametes
- Nourishes gametes
- Transports gametes
What are the 2 distinct functions of the reproduction organs?
- Gametogenesis (Spermatogenesis and Oogenesis)
- Secretion of hormones
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
What are the three major hormones secreted by the reproductive organs?
What produces each hormone?
- Testosterone from the Leydig Cells in the interstitial Tissue
- Oestrogen and Progesterone from the theca and granulosa cells of the Follicle
Is testosterone solely present in men and oestrogen/progestrone solely in women?
No there is lots of overlap between these hormones between sexes
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
What are the [2] reproductive functions of the male system?
- Spermatogenesis
- Delivery of sperm to the female
The female reproductive system is much more complex.
What are the [6] major reproductive functions of the female system
- Oogenesis
- Reception of sperm (at the right time)
- Fertilization
- Gestation
- Parturition
- Lactation
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
Define gametogenesis
The process in which precursor cells (diploid) undergo meiosis to form gametes - the reproductie cells (haploid cells) .
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?
- Firstly, mitotic divisions increase the number of germ cells present
- Meiosis produces
- A Primary gamete
- A secondary gamete
- A mature haploid gamete
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.
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.
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
Describe the process of spermatogenesis:
- Spermatogonium undergos mitosis into 2 identical daughter cells.
- One of the daugther cells (called spermatogonia) will undergo mitosis (proliferate) to form primary spermatocytes
- Primary spermatocytes undergo the first meiosis (this is where the diploid cell becomes haploid) to form secondary spermatocytes
- Secondary spermatocytes undergo a second meiosis to form a spermatid
- The spermatid undergoes packaging and maturation to form the mature spermatozoa
- Spermatozoa slough off the surface of the tubule into the lumen.
From what cell is the major source of testosterone in males?
From Leydig cells (interstitial cells)
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.
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
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.
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
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
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
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
Label the following diagram
