Reproductive System Lecture 1 Flashcards
The Anatomy and Physiology of the Male and Female Reproductive Systems (Chapters 27 & 28) Lecture 1
Male Reproductive System:
Produce and deliver sperm for fertilization.
Produce male hormones (testosterone) for secondary sexual characteristics and reproductive functions.
Female Reproductive System:
Produce eggs (ova) for fertilization.
Provide a site for fertilization and fetal development.
Produce female hormones (estrogen, progesterone) for menstrual cycles, pregnancy, and secondary sexual characteristics.
What You Need to Understand Before Studying the Anatomy and Physiology of the Reproductive Systems:
Basic human anatomy (organs involved in reproductive processes).
Endocrine system (hormonal regulation and feedback loops).
Cell division and gametogenesis (spermatogenesis in males and oogenesis in females).
Genetics (chromosomes and inheritance).
Cyclical vs. Steady Reproductive Systems:
Female System (Cyclical):
The female system undergoes monthly cycles (menstrual cycle) controlled by hormonal fluctuations.
Involves ovulation, menstruation, and changes in the uterine lining.
Influenced by fluctuations in estrogen and progesterone levels.
Male System (Steady):
The male reproductive system produces sperm and testosterone consistently, without cyclical fluctuations.
Sperm production (spermatogenesis) is continuous, with daily sperm production over a long lifespan.
Testosterone levels are relatively constant (though they do fluctuate slightly over the course of a day).
Key Differences Allowing Female System to Be Cyclical and Male System to Be Steady:
Female Cyclical System:
Hormonal fluctuations (estrogen and progesterone) regulate the cycle, causing periodic changes in ovulation, menstruation, and uterine preparation for pregnancy.
The presence of an ovary and its release of eggs trigger specific cycles of hormonal production.
Male Steady System:
Male sperm production is ongoing, driven by constant secretion of testosterone and the continuous process of spermatogenesis.
No need for cyclical hormone surges as in females because sperm production is not tied to a reproductive cycle.
Anatomy of the Male Reproductive System:
Testes:
Located in the scrotum, outside the abdominopelvic cavity at the root of the penis.
Divided by a midline septum into two compartments.
Temperature Regulation:
Testes are 30°C cooler than body temperature, which is crucial for spermatogenesis (sperm production).
Ovaries vs. Testes:
Ovaries are inside the abdominopelvic cavity, while testes are external.
Importance of Temperature:
Cooler temperature is necessary for proper sperm development.
Tunics of the Testes:
Tunica Vaginalis: Outer, 2-layered membrane from the peritoneum.
Tunica Albuginea: Fibrous capsule, divides testis into lobules with seminiferous tubules (ST) for sperm production.
Dartos & Cremaster Muscles in Temperature Regulation:
Dartos Muscle: Contracts in cold to wrinkle and pull testes closer; relaxes in heat to loosen and cool them.
Cremaster Muscle: Pulls testes closer in cold, relaxes in heat to drop them for cooling.
Testicular Descent:
Testes descend from the abdominopelvic cavity into the scrotum before birth.
Seminiferous Tubules:
Seminiferous tubules (ST) are arranged to avoid overlap, ensuring proper sperm production.
Pathway of Sperm to the Ductus (Vas) Deferens:
Seminiferous Tubules: Sperm is produced here.
Tubulus Rectus (Straight Tubule): Sperm moves from seminiferous tubules to the rete testes.
Rete Testes: Network of tubules that collect sperm from seminiferous tubules.
Efferent Ductules: Carry sperm from the rete testes to the epididymis.
Epididymis: Sperm matures and is stored here before moving to the ductus deferens.
Leydig Cells:
Leydig Cells: Interstitial cells located between seminiferous tubules that produce androgens (testosterone).
Meaning of “Interstitial”:
Interstitial means “in between” structures. In this case, Leydig cells are located between the seminiferous tubules.
Blood Supply:
Testicular Arteries: Branch from the abdominal aorta to supply blood to the testes.
Testicular Veins: Form the pampiniform plexus, a network of veins around the testicular artery.
Pampiniform Plexus Role:
Cools the blood in the testicular artery before it reaches the testes to maintain a lower temperature for sperm production.
Spermatic Cord:
Contains blood vessels, lymph vessels, nerves, and the vas deferens.
Sperm Pathway from Epididymis to Exterior:
Epididymis:
Head: Receives sperm from the rete testis.
Body & Tail: Sperm mature over 20 days and gain motility.
During Ejaculation:
Smooth muscle contracts, propelling sperm into the vas deferens.
Sperm Not Ejaculated:
Stored for 2-3 months in the epididymis, after which they are recycled if not ejaculated.
B. Ductus (Vas) Deferens:
Length: ~45 cm long.
Pathway:
Travels from the epididymis to the ejaculatory duct.
The ejaculatory duct passes through the prostate gland into the urethra.
Propels sperm out during ejaculation.
Vasectomy:
A method of birth control where the vas deferens is cut or blocked to prevent sperm from reaching the urethra.
Risks: Infection, bleeding, and possible long-term pain, but it’s generally a safe procedure.
C. The Urethra:
Function: Serves both urinary and reproductive functions.
Regions:
Prostatic urethra
Intermediate part
Spongy urethra
A. Seminal Vesicles (2):
Location: Behind the bladder.
Function: Contribute 70% of semen, with fructose for sperm energy and enzymes for motility.
Yellow color: From flavin proteins.
Sperm swim in the female reproductive system after ejaculation.
B. Prostate Gland (1):
Location: Chestnut-shaped, encircles the urethra beneath the bladder.
Function: Produces milky secretion (1/3 of semen), containing enzymes and PSA to activate sperm.
Bulbourethral Glands (2):
Location: Pea-sized, below the prostate.
Function: Secrete clear mucus to clean urine traces and provide lubrication before ejaculation.
Prostate Issues: Enlarged prostate can block the urethra; PSA levels indicate prostate problems.
Penis Structure:
Function: Delivers sperm into the female reproductive tract.
External: Composed of penis and scrotum.
Root: Attached to the body.
Shaft: Main length.
Glans Penis: Enlarged tip.
Foreskin/Prepuce: Skin around the glans (removed in circumcision).
Internal Structure:
Spongy Urethra: Part of the urethra in the penis.
3 Corpora:
2 Corpora Cavernosa: Paired dorsal tissues.
1 Corpus Spongiosum: Midventral tissue, forms glans and bulb.
Composition of Semen:
Functions:
Transport medium for sperm.
Nutrients like fructose and citrate.
Chemicals (e.g., PGs, ATP, antibiotics) to protect and activate sperm.
pH: 7.2-7.6, neutralizes vaginal acidity.
Volume: 2-5 ml per ejaculation.
Sperm Concentration: 50-100 million/ml.
5.2.1 Sertoli vs. Leydig Cells:
Sertoli Cells:
Located in seminiferous tubules, support spermatogenesis.
Make up 80% of testicular mass.
Leydig Cells:
Found between seminiferous tubules.
Produce testosterone (androgens).
Additional Info:
Sperm production rate: 200 million/day.
Testes produce germ cells (sperm) and hormones (testosterone).
Steroid Hormones:
Cholesterol-derived, lipid-soluble (e.g., Testosterone).
Regulate gene expression.
Amino Acid-Based Hormones:
Amino acid-derived, water-soluble.
Trigger signaling via cell surface receptors.
Testosterone Synthesis:
Leydig Cells produce testosterone.
Actions of Testosterone:
Gonadal:
Growth/maturation of gonads and accessory organs.
Essential for spermatogenesis.
Somatic:
Growth spurts.
Larynx & vocal cord growth.
Sweat secretion.
Hair growth (face, chest, groin).
Metabolic:
Anabolic effects (hematopoiesis, BMR).
CNS:
Libido.
Aggression.
First Event:
Gonadal growth/maturation starts first.
teroid Hormone Action:
Diffusion: The steroid hormone diffuses through the plasma membrane.
Binding: It binds to an intracellular receptor.
Nuclear Entry: The receptor-hormone complex enters the nucleus.
DNA Binding: The complex binds to a specific region of DNA.
Transcription: This binding initiates transcription of the gene into mRNA.
Protein Synthesis: The mRNA directs protein synthesis.
Hypothalamic & Pituitary Regulation of Steroidogenesis:
Gonadotropins (FSH & LH) are glycoproteins and water-soluble, binding to cell surface receptors to regulate enzymes.
FSH: Stimulates Sertoli cells for spermatogenesis (requires testosterone).
LH: Stimulates Leydig cells to secrete testosterone.
GnRH & Inhibin Regulation:
GnRH: Stimulates FSH and LH release.
Inhibin: Released by Sertoli cells, inhibits FSH secretion.
Why Helpful?
Inhibin helps regulate sperm production by balancing FSH levels.
See the diagram
Regulation of testosterone production and secretion by the hypothalamic-pituitary-testicular axis
See the diagram
See last slide
