Lecture 21 - Sperm Production and Delivery Flashcards
Internal genitalia of a male
Testes (gonads) —> make sperm
Series of ducts and glands —> helps with maturation of the sperm or secrete fluids to help keep sperm viable. They support and move sperm to the external genitalia
External genitalia of a male
Urethra and penis —> deliver sperm
Scrotum —> keeps the testes outside the abdominopelvic cavity for temperature regulation
Function of male reproductive system
Manufacture sperm (gametes) and to deliver them to an ovum in viable form
Function of urethra and penis in male reproductive system
Responsible for depositing sperm in female reproductive tract and ofc pleasurable sensations ;)
What are the 3 parts that make up the scrotum? What is its function?
Skin, dartos muscle and superficial fascia
Used to support testes
Where is sperm produced?
From germ cells within the seminiferous tubules of the testes
What is spermatogenesis and what are its 4 cellular stages?
The process of generating sperm from spermatogonia. 4 cellular stages:
- Spermatogonium
- Spermatocyte
- Spermatid
- Sperm
What does gametogenesis involve?
Gametogenesis (including spermatogenesis) involves meiosis as well as mitosis
Meiosis is when a dividing germ cell splits its paired chromosomes between its offspring, rather than duplicating them
Total time needed to complete the stages of spermatogenesis
~2 months
Time needed for each stage of spermatogenesis
Meiosis of a spermatogonium - 16 days
Meiosis I - 24 days
Meiosis II - hours
Spermatogenesis (physical maturation) - 24 days
Total ~64 days
Describe the movement of spermatogenesis
As developing gametes progress from spermatogonium -> spermatocyte -> spermatid -> sperm, they move from the basal layer of the seminiferous tubule towards the lumen, while maintaining contact with the Sertoli cells
Structure of a sperm
- Acrosome (tip): contains enzymes needed to penetrate an ovum during fertilization
- Head: contains haploid chromosomes
- Neck
- Middle piece: contains mitochondria which generate ATP to keep the tail moving
- Tail: flagellum; a motile organelle that moves the sperm
True or False. An anatomically mature sperm is functionally (physiologically) mature.
False. When a sperm detaches from the Sertoli cells and enters the rete testes, it has all structures but it is still incapable of going through the process of fertilization
What occurs in the epididymas and what do epididymal cells secrete? How does it affect the sperm maturation process? What is the transit time through the epididymis?
Physiological maturation of sperm. It secrets immobilin which keeps sperm immotile
It secrete factors which promote maturation process resulting in:
- Compaction of genetic material
- Alteration of sperm plasma membrane
- Maturation of the acrosome proteins
Transit time of sperm through the epididymis is 10-15 days
Where do sperm travel through, where they can also be stored?
Transported from the epididymis to the vas deferens/ductus deferens
While sperm travel through the vas/ductus deferens they are inactivated and can be stored this way in the ampulla for several months
Capacitation
The process by which sperm become motile and are capable of fertilization (ie. can penetrate the cell membrane of an ovum)
The first stage of capacitation (motility) occurs in the ejaculatory duct when sperm mix with seminal fluid that is secreted from seminal glands (vesicles)
How do the autonomic and somatic nervous systems influence penile tissue?
Parasympathetic fibres - innervate the erectile tissue. During arousal, relaxes smooth muscle in this tissue, allowing increased blood flow that fills that vascular spaces, causing an erection
Sympathetic fibres - innervate the epididymis, vas deferens, and seminal vesicles. When activated, sperm and secretion are moved into the urethra
Lumbosacral somatic motor neurons - innervate the skeletal muscles at the base of the penis. During ejaculation, spinal reflex produces rhythmic contractions in these muscles (aka orgasms), which helps push semen out the urethra
How does HPG axis regulation affect the male reproductive system
GnRH is secreted from the hypothalamus, creating pulses of increased LH and FSH secretion from the anterior pituitary
*if the rhythm of pulsatile GnRH secretion is disrupted, testicular functions are impaired
How do gonadal hormones cooperate to regulate sperm production?
- Leydig cells: activation directs androgen synthesis and release
- Sertoli (nurse) cells: activation promotes spermatogenesis and also produce inhibin, a regulatory hormone
Sertoli cells also enhance sperm function in many ways:
- Maintain the blood-testis barrier
- Maintain spermatogonia numbers
- Direct spermatocytes to complete meiosis
- Promote adhesion and development of spermatids
How do gonadal hormones provide negative feedback to the HPG axis?
Androgenic negative feedback mostly occurs at the hypothalamus
Inhibin has a major role in inhibiting the secretion of gonadotropes (FSH and LH) found in the anterior pituitary
