Biology Reviewer: Reproductive System

Biology Reviewer: Reproductive System by: dadang Human Male Reproductive System 1. External Organs: ○ Scrotum: A fold of skin that holds the testes and keeps them cooler than body temperature (about 2°C cooler), which is important for sperm production....

Biology Reviewer: Reproductive System by: dadang Human Male Reproductive System 1. External Organs: ○ Scrotum: A fold of skin that holds the testes and keeps them cooler than body temperature (about 2°C cooler), which is important for sperm production. ○ Penis: Contains the urethra and spongy erectile tissue. During sexual arousal, this tissue fills with blood, causing an erection. This allows the penis to be inserted into the vagina. 2. Internal Organs:  ○ Testes: Also called testicles. They produce sperm in coiled tubes called seminiferous tubules. Sperm production works best at lower temperatures, which is why the testes are outside the body in the scrotum. ○ Seminiferous tubules: Coiled tubes inside the testes where sperm are produced. These are the main sites of sperm formation in the male reproductive system. Testicle: A testis inside the scrotum. In some animals, the testes can move back into the abdomen during non-breeding seasons. ○ Epididymis: A coiled tube where sperm mature and become able to swim (motile). Sperm takes about 3 weeks to travel through it. ○ Vas Deferens: A tube that carries sperm from the epididymis around the bladder during ejaculation. The vas deferens joins the seminal vesicles' duct to form the ejaculatory duct, which opens into the urethra. ○ Urethra: The tube that carries both urine and sperm outside the body through the penis. 3. Accessory Glands: ○ Seminal Vesicles: Two glands that produce 60% of semen, which includes mucus, fructose (sugar for sperm energy), enzymes, and prostaglandins (local regulators). ○ Prostate Gland: Secretes a thin, milky fluid with enzymes and citrate (a nutrient for sperm). ○ Bulbourethral Glands: Secrete clear mucus before ejaculation that neutralizes acidic urine in the urethra. This fluid may contain sperm, which can lead to pregnancy even before full ejaculation. 4. Penis and Erectile Function: ○ The penis contains erectile tissue that fills with blood during arousal, causing an erection. This is needed for insertion into the vagina during intercourse. ○ Erectile Tissue: Spongy tissue in the penis (or clitoris) that fills with blood during sexual arousal, causing the tissue to harden and enlarge, leading to an erection. ○ Erectile Dysfunction (ED): Can be caused by alcohol, drugs, emotions, or aging. Drugs like Viagra help by increasing blood flow. ○ Some mammals, like dogs and raccoons, have a bone in their penis called the baculum for extra stiffness. Human Female Reproductive System 1. External Organs: ○ Clitoris: A sensitive erectile organ at the top of the vulva. ○ Labia Majora and Minora: Skin folds around the vaginal opening and clitoris. 2. Internal Organs: ○ Ovaries: The female gonads, which produce eggs and hormones. Each ovary contains many follicles, which hold immature eggs (oocytes). ○ Oocytes: A partially developed egg, surrounded by support cells. ○ Oviduct (Fallopian Tube): A tube that carries eggs from the ovary to the uterus. Cilia (tiny hairs) help move the egg along. ○ Uterus (Womb): A thick, muscular organ that can expand to hold a developing baby. The inner lining is called the endometrium, which is rich in blood vessels.  ○ Endometrium: The inner lining of the uterus, which is rich in blood vessels. It thickens during the menstrual cycle to prepare for a possible pregnancy and is shed during menstruation if no pregnancy occurs. ○ Cervix: The lower part of the uterus that opens into the vagina. ○ Vagina: A muscular, elastic tube that receives the penis during intercourse and acts as the birth canal. 3. Vulva: ○ Vulva: The external genitalia, which includes the labia and clitoris. ○ Hymen: A thin tissue that may partly cover the vaginal opening at birth, but often wears away through physical activity. ○ During arousal, the clitoris, labia minora, and vagina become engorged with blood. Vestibular glands produce lubricating mucus. 4. Mammary Glands: ○ Present in both males and females, but only active in females. These glands produce milk to feed babies. Gametogenesis (Formation of Sex Cells) 1. Spermatogenesis (in males): ○ Happens continuously from puberty through adulthood. Millions of sperm are produced every day, and it takes about 7 weeks for a sperm cell to fully mature. 2. Oogenesis (in females): ○ Starts before birth but is not completed until later in life (sometimes decades). Only one mature egg is produced from each cell, while the other cells (called polar bodies) degenerate. ○ Female eggs mature slowly and stop being produced around age 50. Key Differences Between Spermatogenesis and Oogenesis: Spermatogenesis: Continuous production of sperm throughout life. Four sperm are made from one cell during meiosis. Oogenesis: Occurs with long breaks, starting before birth. One egg is produced from each cell, with the rest becoming non-functional polar bodies.