Male Reproduction System Flashcards
What is the male reproduction system composed of?
The Male reproduction system is composed of:
- Penis
- Testes
- Genital ducts
- Accessory glands
What is the function of the male reproductive system?
The function of the male reproductive system is to produce hormones and sperm
Describe the generation of sperm starting with the stem cell and ending with sperm. Denote whether the cell is haploid or diploid
Spermatogonium (2N) -> 1° Spermatocyte (2N) -> 2° Spermatocyte (N) -> Spermatid (N) -> Sperm (N)
What temperature does spermatogenesis occur?
- Spermatogenesis occurs only below 37°C.
- The Scrotal Sac maintains a temp of 34°C
What are the male gonads and where are they located?
The male gonads are the testes and they are located in the scrotum
Describe the structure of the testes
The testes consist of:
- tubules called seminiferous tubules (spermatozoa form here)
- The seminiferous tubules are surrounded by loose connective tissue rich in blood vessels, lymphatics, nerves, and Leydig cells
- Leydig cells produce testosterone
What is a Leydig cell?
A Leydig cell surrounds the seminiferous tubules in the testes and produces testosterone
- Testosterone is a steroid derived from cholesterol
- They have a large accumulation of Smooth ER to aid in steroid formation
- They have a well developed golgi apparatus for quick exocytosis of hormones
- Leydig cells also release other androgens like androstenodione and dehydroepiendrosterone
What are the seminiferous tubules?
The seminiferous tubules are located in the testes
- Spermatozoa is formed here.
- About 1000 seminiferous tubules are found in the two testes
What are the two types of cells found in the seminiferous tubules?
Two types of cells in the seminiferous tubules:
- spermatogenic cells: These generate sperm
- Sertoli cells: These are the “nurse” cells
What is a Sertoli Cell?
A Sertoli cell is a special cell type found in the seminiferous epithelium
- These are the “Nurse Cells” of the seminiferous tubules
- They protect, support, and give nourishment to the spermatogenic cells.
- Sertoli cells also do a bit of phagocytosis of cytoplasm eliminated during the production of sperm
Describe the roles of hormones in testosterone synthesis and spermatogenesis.
- At puberty, the hypothalamus begins the production of gonadotropin-releasing hormone (GnRH)
- GnRH tells the anterior pituitary gland to secrete LH and FSH
- LH causes the Leydig cells to secrete testosterone
- FSH binds to the Sertoli Cells and aids in spermatogenesis
What are the hormonal negative feedback loops of the male reproductive system?
The hormonal negative feedback loops of the male reproductive system are as follows:
- Elevated levels of testosterone in the blood prevents the secretion of for GnRH
- High sperm count causes Sertoli cells to secrete inhibin which inhibits the production of FSH
What is the testis?
The testis is one of the testes
- this is where sperm production occurs
What is the epididymis?
The epididymis surrounds the testes and is where the maturation of sperm occurs. Sperm attain:
- maturation
- motility
- membrane receptors for the zona pellucida protein (egg membrane protein)
- acrosomal maturation (tip of the sperm where degradative enzymes are found)
What is the prostate gland?
The prostate gland:
- Secretes and stores a significant contribution to the seminal fluid
- The fluid is slightly alkaline to help neutralize the acidic environment of the vagina
- Contains smooth muscle that helps expel semen during ejaculation
- Common site for cancer in men over 65
Describe prostate cancer and some possible interventions
The prostate is a common site for cancer in men over 65
- A normal product called prostate specific antigen (PSA) is usually elevated in the blood during malignancy. This is a useful test for doctors
- Prostate cancer is usually stimulated to grow more rapidly by testosterone and inhibited by estrogen.
- One possible treatment is to remove the testes (where testosterone is produced) and administer estrogen.
What is the vas deferens?
The Vas Deferens is the tube that conveys the sperm from the epididymis to the ejaculatory duct
What is the ejaculatory duct?
The ejaculatory duct holds sperm prior to ejaculation and empties it into the urethra.
What are the accessory glands?
Accessory glands are glands that add secretions to the semen in addition to what’s secreted by the prostate. They include:
- Bulbourethral glands (Cowper’s glands)
- Seminal Vesicles
What are the seminal vesicles?
The seminal vesicles are accessory glands that add secretions to the semen. The secretions make up
about 60% of the semen volume and include:
- amino acids
- proteins
- prostaglandins
- Vitamin C
- fructose (This is the main constituent, it provides the fuel needed for the very motile sperm. NB for the DAT)
What is the main constituent of seminal vesicle secretions?
fructose is the main constituent of seminal vesicle secretions, it provides the fuel needed for the very motile sperm. NB for the DAT!
What is the Bulbourethral Gland?
The Bulbourethral gland is an accessory gland that secretes:
- thick mucus that aids in neutralizing any acidic urine in the urethra and also aids in lubricating the urethral lining
- This is what pre-cum is. It also can carry some sperm cells, so you can get pregnant even without ejaculation
What is the pH of semen when it leaves the urethra?
The pH of semen as it enters the vagina is 7.5
Describe the head of a mature sperm cell
The head of a mature sperm cell:
- contains the nucleus
- surrounded on the anterior end by the acrosome
- connects to the neck which contains centrioles
What is the acromosome?
The acrosome surrounds the head of a mature sperm on the front of it.
- contains the digestive enzymes (hyaluronidase and acrosin) that will be involved with breaking down the zona pellucida
- derived from the golgi, the acrosome is actually an organelle
- Upon contact with the jelly coat of the egg, exocytosis from the acrosome is triggered releasing the digestive enzymes that drill a hole in the egg.
What are the 3 main processes of fertilization?
The three main processes of fertilization are:
- Acrosomal reaction: hydrolytic enzyme release
- Cortical reaction: hardening of jelly coat to prevent potential polyspermy
- Capacitation: Biochemical changes that allow the sperm to swim better
What is in the neck of the sperm?
The neck of the sperm contains the sperm centrioles that connect the head to the midpiece.
What is in the midpiece of the sperm?
The midpiece of the sperm contains many mitochondria which provide energy for the sperm movement
What is the tail of the sperm?
The tail of the sperm is actually a flagellum.
- 9 + 2 microtubule arrangement (Called an Axoneme)
- ATP provided by the midpiece helps fuel dynein, which uses ATPase activity to propel the flagellum
What is dynein?
Dynein is a family of motor proteins involved with transport and providing forces during mitosis.
- These proteins are the main motors of sperm motility.
How does progesterone in the vagina affect sperm?
Progesterone secreted by the egg into the vagina gives sperm an energy boost to help it swim faster.
- it activates a ca++ channel called CATSPER that somehow increases motility.
- This has recently been discovered and not much is known still
Do any animals have internal testes?
YES!
Whales and dolphins internal body temperatures are low enough to have their testes be internal
What part of the sperm enters the egg upon fertilization?
The ENTIRE sperm cell from head to tail enter the egg cell.
What part of Dad’s DNA is lost?
Dad’s mitochondrial DNA is lost. All the DNA you have in your mitochondria is inherited from your mother.
