Testes Flashcards
What does the male reproductive system develop from?
The mesonephric duct and collecting duct tubules of the mesonephros, due to expression of the SRY gene.
What are the three accessory glands to the male reproductive tract?
Prostate gland, seminal vesicles, bulbo-urethral glands.
What are the two roles of the testes?
Produce sperm
Produce androgens
Where do all the highly convoluted seminiferous tubules connect?
To the rete testis in the mediastinum testis, which then empties into the head of the epididymis.
What are the seminiferous tubules packed into within the testis?
Lobes
Why is it important that sperm are kept in the testis for a period of time?
So they can mature.
Which cells line the seminiferous tubules, and which cells are interstitial between the seminiferous tubules?
Sertoli cells line the seminiferous tubules and have tight junctions between then to form the blood-testes barrier. Leydig cells are outside of the basement membrane, in-between the seminiferous tubules.
What are the three layers of cells in the wall of the seminiferous tubule?
MYOID cells form a layer of smooth muscle cells outside the basal lamina.
BASAL LAMINA between the myoid cells and sertoli cells.
SERTOLI cells form inner epithelial layer.
What is the general role of the Sertoli cells?
Sustenacular cells which nuture the sperm and regulate development. They also have tight junctions to form the blood-testis barrier to prevent an immune response against the spermatozoa.
What happens to the blood-testes barrier in the absence of androgens?
It degrades. Androgens are required for a functional blood-testes barrier.
During prophase 1, what are the sites called where homologous chromosomes swap sections of the chromatids (crossing-over)?
Chiasmata
What is different about the cell division in an oocyte compared to mitosis?
The cell division is UNEQUAL, so a polar body is formed and the oocyte receives most of the cytoplasm.
What is different about the cell division in a spermatocyte compared to mitosis?
The cell division is INCOMPLETE, so the spermatids are still linked by cytoplasmic bridges.
What are the three phases of spermatogenesis?
Mitotic proliferation (produces large numbers of cells) Meiotic division (produces genetic diversity and halves the chromosome number) Cytodifferentiation (package chromosomes for effective delivery to the oocyte)
What do mitotically arrested prospermatogonia become when they restart mitosis in puberty?
Spermatogonial stem cells (SSCs)
How many times can each spermatogonial stem cell divide by mitosis, and what do they produce?
Each SSC can divide up to 4 times and produce a Spermatogonium Type A1. So each SSC has the potential to produce 16 clones (Type A1 spermatogonia)
How many more mitotic divisions does each Type A1 spermatogonium undergo to reach the Type B spermatogonium, and what is produced at each step?
Type A1 spermatogonium undergoes 5 more mitotic divisions.
Type A1 spermatogonium -> Type A2 spermatogonium -> Type A3 spermatogonium -> Type A4 spermatogonium -> Intermediate Spermatogonium -> Type B spermatogonium
What does a Type B Spermatogonium divide mitotically to produce?
Resting primary spermatocyte
What two things happen when the resting primary spermatocyte is produced?
Mitosis stops
The resting primary spermatocyte had to breach the blood-testes barrier by pushing its way through the tight junction to move from the basal compartment to the luminal compartment.
Why are the testes outside of the body cavity?
They are maintained at a slightly lower temperature than core body temperature, this could be because the very high rate of cell division produces a lot of excess heat.
What stage of the cell cycle are prospermatogonia in until puberty?
Interphase.
What happens when the primary spermatogonia enter the luminal compartment?
They complete meiosis I to form secondary spermatocytes (haploid). Secondary spermatocytes then complete meiosis II to form spermatids.
What is the name for the cytodifferentiation where the spermatids change shape from round to elongated, and develop a tail for motility?
Spermiogenesis.
What happens to the Golgi body in spermiogenesis?
The Golgi apparatus migrates to one pole and forms the lysosomal like granules that coalesce to form the acrosome. The acrosome grows over the nuclear surface like a cap.
