Male Reproductive System: Anatomy and Fertility

• Lesson 1 explores the male reproductive system and factors affecting male fertility.
• Key questions include the main structures and functions, how these structures support human continuity, the functional unit, sperm cell development, and supporting structures for gamete development.

Anatomy of the Male Reproductive System

• Understanding the anatomy and physiology of the male reproductive system including primary reproductive organs, ducts, and accessory glands, is important for reproductive health.
• Reproduction ensures the species' survival and continuity.
• The reproductive system becomes functional during puberty, influenced by hormones.
• Reproduction highlights sex differences and is crucial for species perpetuation.
• Internal fertilization in vertebrates protects the developing embryo.
• Fewer eggs lead to longer offspring nurturing periods after birth.
• Infertility is the inability to reproduce.
• A gamete is a haploid cell from meiosis that participates in fertilization to make a zygote.
• An embryo is the offspring during development from zygote cleavage to the ninth week, when it becomes a fetus.

Functions of the Male Reproductive System

• The male reproductive system performs sperm production, releases hormones like androgens, and deposits sperm into the female reproductive system.
• Androgens are a group of male steroid hormones, including testosterone.

Structures of the Male Reproductive System

• Sperm cells are the smallest human cells but much smaller than the female egg.
• Sperm size differences are related to cytoplasm amount.
• Each sperm has half the genetic material needed for reproduction (23 chromosomes), while normal body cells contain 46 chromosomes.
• Ejaculation releases 200 to 400 million sperm, though only one fertilizes an egg.
• Sperm use a tail (flagellum) for mobilization.
• Genetic material is DNA containing genes for protein synthesis as chromatin or chromosomes.
• Ejaculation is the semen release from the penis.
• Seminiferous tubules are coiled tubes in the testes where sperm production occurs.
• Testes are paired male gonads that produce sperm and secrete testosterone.
• The scrotum, a skin pouch below the penis, holds the testes.
• Sperm production requires a temperature 3°C below body temperature, which the testes maintain outside the body.
• In cold conditions, the scrotum contracts, pulling testes closer to the body.
• In warm conditions, the scrotum expands, lowering testes away from the body.
• The epididymis, a coiled tube atop each testis, matures and mobilizes sperm over 10 to 14 days, after developing for 64 to 72 days in the seminiferous tubules.
• Environment includes non-genetic factors like upbringing, light, friends, temperature, experiences, diet, etc.
• Semen exists the testes through the vas deferens.
• A vasectomy blocks sperm passage, preventing conception.
• The vas deferens is a smooth muscle tube carrying semen from the epididymis to the penis.
• As sperm exit the testes, they mix with seminal fluid from accessory glands, provide an alkaline to protect sperm, and counteract acidic conditions.
• The urethra leading from the bladder and vagina contain acidic environments.
• Seminal fluid nourishes sperm, allowing survival for 2-3 days.
• Seminal vesicles, prostate gland, and Cowper's gland produce seminal fluids.
• Sperm typically survive at normal body temperature for 24 to 72 hours.
• The urethra is the tube leading from the bladder to the penis.
• The vagina leads from the uterus to the external environment.
• Seminal vesicles produce nutrient-rich fluids like fructose to sustain sperm.
• The prostate gland and Cowper's gland secrete mucus and alkaline fluid, neutralizing acids and lubricating.
• Semen contains components to protect and nurture sperm.
• Semen is the ejaculated liquid with sperm and seminal vesicle, prostate, and Cowper's gland secretions.
• Nurture is the environmental component of phenotypes.
• Sperm do not enter the accessory glands (seminal vesicles, prostate gland, Cowper's gland); instead, these glands secrete fluid to form the semen which transports the sperm.

Spermatogenesis

• Spermatogenesis is the formation of sperm.
• Oogenesis is the formation of eggs.
• Gametogenesis is the process of creating gametes from somatic cells and includes meiosis.
• Sperm production occurs continually in males, while females are born with all eggs they will have.
• Lifestyle choices impact sperm quality, with quality declining after age 25.
• Mature sperm are spermatozoa, closely associated with Sertoli and interstitial cells.
• Sertoli cells, located in seminiferous tubules, nurture sperm and act as a protective barrier.
• The body recognizes spermatozoa as foreign, requiring Sertoli cells' protection.
• Interstitial cells in testes secrete testosterone, stimulating male reproductive system development, secondary sex characteristics, and spermatogenesis, however are not located in the seminiferous tubules.
• Spermatid are haploid cells resulting from meiosis that swim to the epididymis for maturation to a spermatozoan and storage until ejaculation.
• Spermatozoa are mature sperm stored in the epididymis,
• Sertoli cells ('nurse cells') in seminiferous tubules assist in spermatogenesis and produce the hormone inhibin.
• Interstitial cells are tightly packed testosterone-secreting cells around seminiferous tubules in the testes.
• Sex characteristics are structures differentiating males from females.

Male Reproductive System Primary Components

• Testes produce and store sperm, testosterone, and inhibin
• The epididymis sores sperm, providing location for maturation.
• The penis transfers semen to females.
• The urethra transports both semen and urine.
• The vas deferens transports sperm from the seminiferous tubules to the urethra.
• The urinary bladder is where urine is stored and emptied into the urethra.
• The Ureter transports urine from the kidney to the bladder.
• The seminal vesicle secretes mucus which includes fructose which is used as energy for the sperm.
• The prostate gland secretes mucus and alkaline fluid to neutralize the acidic conditions of the urethra and vagina.
• The Cowper's gland secretes mucus and alkaline fluid to neutralize the acidic conditions of the urethra and vagina.
• Gonads are sex organs that produce gametes (sperm or egg)
• Inhibin is a hormone produced by Sertoli cells during spermatogenesis that inhibits GnRH, preventing excessive sperm protection.