Flashcards in Endo-Repro L13 Male 2 Deck (40):
• Mitotic proliferation → spermatogonia
• Meiotic division → Primary spermatocyte
• Spermiogenesis → round serpmatid – elongated spermatazoa
Releasing sperm from Sertoli cell
Spermatogenesis within seminiferous tubule epithelium: Definition
Process by which Type A dark spermatogonia (the main stem cell in the seminiferous tubule) form spermatozoa.
Spermatogenesis within seminiferous tubule epithelium: Involves three stages
1. Mitotic proliferation to (Type A light is converted to Type B) produce large reservoir of identical cells (spermatogonia proliferate and form primary spermatocytes).
2. Meiotic division to give rise to haploid gametes and increase genetic diversity (primary spermatocytes undergo meiosis to form spermatids)
3. Spermiogenesis or cytoplasmic remodelling to produce specialised germ cells (spermatids form spermatozoa).
Committed cell to spermatogenesis
Type A Dark
Stem cell replaces sperm
Type A light
Transformed SC = divide to form Type B
Stages of spermatogenesis:
1. Type A: Spermatogonium (Dark) converted to Spermatogonium
a. Some divide to replenish pool of Type A Dark (replaces pool)
2. Type A: Spermatogonium (light) is converted to a Type B spermatogonium (committed to differentiate).
Primary spermatocyte formed and undergoes meiosis.
1. Primary spermatocyte converted to secondary spermatocyte
2. Forms a spermatid converted into a spermatozoon
Dynamics of spermatogenesis:
1. Highly organised process: temporally and spatially to ensure a continual production of sperm
2. Whole process (Type A dark to spermatozoon) takes about 64 days in the human)
3. In a given area, Type A dark spermatogonia initiate a new wave of spermatogenesis every 16 days.
4. It is a long process therefore the epithelium will contain four successive batches (cohorts) of cells progressing through spermatogenesis at any one time
5. The progression of these four batches is highly organised, and each patch of epithelium goes through a 16-day cycle recognised by particular cell associations.
6. To avoid cyclic sperm production, adjacent patches of seminiferous epithelium initiate spermatogenesis at different times (i.e. they are not synchronised).
1. Formation of Acrosome, flagellum and mid-piece.
2. Loss of excess cytoplasm
a. Form acrosome (head)
b. Cap formation
c. Form midpiece (mitochondria)
Roles of Sertoli cells:
1. Under FSH regulation
2. Provides physical and metabolic support for developing spermatizia
3. Form the blood-testis barrier (prevents autoimmunity and toxic damage)
4. Secrete anti-lymphocytic factors – protection.
5. Resorb leftovers from spermiogenesis
6. Secrete and maintain ion composition of seminiferous tubular fluid.
7. Secrete inhibin
8. Make androgen binding protein
9. Involved in steroid conversion (e.g. convert testosterone to DHT).
Spermatogenesis is dependent upon
Both pituitary gonadotrophins (i.e. LH and FSH)
Leydig cells to maintain testosterone secretion
FSH targets Sertoli cells to
Maintain their function
Feedback regulation of LH is
Feedback regulation of FSH is via
Storage of sperm in epididymis: protected by
Epididymis function is
Highly androgen dependent
Sperm are stored in
Tail of epididymis (at least 10(9) sperm/ml)
Sperm movement is
Sperm undergo final maturation in epididymis (3)
1. Loss of cytoplasmic drop
2. Stabilisation of cell membrane
3. Increased energy reserve
Sperm survival in epididymis
Non-ejaculated sperm are
Reabsorbed (or lost in urine)
Mechanism of erection:
1. Active dilation of arterial supply to erectile tissue (corpus cavernosa and corpus spongiosum) → Sacral parasympathetic outflow (pelvic nerves).
2. Passive impedance of venous drainage (compression, closure of valves, contractions of ischiocavernosus and bulbospongiosus muscles).
Mechanisms of ejaculation:
1. Seminal emission involves contractions of epididymis and vas deferens to send sperm to ampulla, followed by contractions of prostate, ampulla and seminal vesicles to send semen “mix” to upper urethra.
2. Thoracocolumnar (Sympathetic) outflow) → Hypogastric nerves contractions of vas deferens, seminal vesicle sand prostate = seminal emissions.
3. Sacral (parasympathetic and somatic) outflow contractions of smooth and striated pelvis musculature associated with urethra = ejaculation.
Two phases of ejaculation:
1. Seminal emissions phase involves contractions of epididymis and vas deferens to send sperm to ampulla, followed by contractions of prostate, ampulla and seminal vesicles to send semen “mix” to upper urethra.
2. Ejaculation phase involves contractions of smooth and striated musculature associated with urethra.
Transport vehicle, buffering and nutrient supply.
Constituents of semen
Various enzymes e.g. acid phosphatase
Low sperm count (oligospermia)
May signal a genetic disorder (e.g. azoopermia – complete absence of sperm in the ejaculate.
Low sperm motility
Low semen volume
Endocrine disorders (Hyperprolactinaemia)
Pathological damage of seminiferous epithelium (e.g. mumps)
Chromosomal abnormalities (Klinefelters syndrome)
Presence of antibodies to sperm
High scrotal temperatures
Over frequent or under frequent ejaculation
Obstructive azoospermia (e.g. block to vas)
Poor diet (deficiencies of vitamins A, B or D)
Disorders of seminal plasma (e.g. poor liquefaction)
Inflammation of prostate gland
Benign prostatic hyperplasia (enlargement)
Uniforms, smooth enlargement of gland, normal aging
Prostatic cancer (carcinoma)
Erectile dysfunction Causes