BSC2086 1st Edition Lecture 24 Outline of Last Lecture I. Introduction to the reproductive systemII. Structures of the reproductive systemIII. Male reproductive functions Outline of Current Lecture I. Male Reproductive Functions continuedII. Female Reproductive SystemIII. Structures of Reproductive System IV. Oogenesis V. Ovarian Cycle VI. Uterine Tubes Current Lecture I. Male reproductive functions continued a. Spermatozoon i. Head 1. Has a nucleus and chromosomes2. Acrosome: cap-like compartment found at the tip of the heada. Has enzymes needed for fertilizationii. Neck 1. Attaches head to middle pieceiii. Middle piece1. Has mitochondria which provides ATP to move tailiv. Tail1. ONLY flagellum in the human body2. Whip-like organelle 3. Moves cell from one place to another a. Complex, corkscrew motionv. Mature spermatozoon 1. Does not have:a. Endoplasmic reticulumb. Golgi apparatus c. Lysosomes and peroxisomesd. Inclusions e. Other intracellular structures2. Organelles not present to reduce sperm size and mass3. Plasma membrane contains antigens not present in somatic cells4. Sperm must absorb nutrients such as fructose from the surrounding fluidb. Sperm maturationi. Testes make physically mature spermatozoa which cannot fertilize an oocyteii. Other parts of the reproductive system are responsible for functional maturation, nourishment, storage and transport iii. Spermatozoa 1. Detach from nurse cells 2. Found free in lumen of seminiferous tubules 3. Functionally immature, therefore incapable of locomotion or fertilization4. Moved by cilia into the epididymisiv. Epididymis 1. Start of male reproductive tract 2. Coiled tube almost 7 meters, or 23 feet, long3. Bound to the posterior border of the testes4. Functions to both store and protect spermatozoa received from testes 5. Recycle damaged spermatozoa 6. Monitors/adjusts fluid composition in the seminiferous tubules7. Mature sperm can leave the epididymis but must go through capacitation before they can swim v. Capacitation 2 steps1. Spermatozoa become motile when mixed with seminal gland secretions2. Spermatozoa become able to fertilize an oocyte when exposed to the female reproductive tract 3. The epididymis secretes substances that prevents early capacitation c. Ductus deferens (vas deferens)1. Part of the spermatic cord that starts at the tail of the epididymis 2. Ascends through inguinal canal3. Curves under the bladder toward the prostate and seminal glands4. Lumen enlarges into ampulla5. Wall made of thick layer of smooth muscle which performs peristaltic contractions to propel the spermatozoa and fluid 6. Able to store spermatozoa for several months in a state of suspended animation, where they have low metabolic ratesd. Ejaculatory duct 1. Short passage, 2 cm or less than an inch2. Penetrates the wall of the prostate gland3. Empties into urethra e. Urethra 1. Used by urinary and reproductive system in males 2. 18-20 cm or 7-8 inches long, from the urinary bladder to the tip ofthe penis3. Divided into:a. Prostatic b. Membranousc. Spongyf. Accessory glands i. Makes semen mixture of secretions from many glands 1. Each secretion has a distinctive biochemical characteristic ii. Important glands are:1. Seminal gland2. Prostate gland3. Bulbo-urethral glands iii. Functions of male glands1. Activate spermatozoa 2. Give nutrients to spermatozoa needed motility 3. Propel spermatozoa and fluids along the reproductive tracta. Mainly by peristaltic contractions4. Produce buffers which counteract acidicity of the environments of the urethra and vaginal environments iv. Seminal glands 1. Make seminal fluid which makes up about 60% of semen volume a. Empties into prostatic urethra2. Same osmotic concentration as blood plasma but different composition a. High fructose which is easily metabolized by spermatozoa b. Smooth muscle contractions stimulated by prostaglandins i. In both males and females c. Fibrinogen makes a temporary clot in the vagina 3. Slightly alkaline to neutralize acids in the vagina and prostate gland4. Seminal fluid a. Starts the first step in capacitation i. Spermatozoa start beating flagella and become highly motile b. Discharged into the ejaculatory duct at emission when peristaltic contractions begins c. Sympathetic nervous system controls contractions v. Prostate gland1. Small muscular organ about 4 cm or 1.6 inches in diameter2. Encircles the proximal portion of the urethra found under the bladder3. Surrounded by smooth muscle fibers4. Prostatic fluida. Makes 20-30% of semen volumeb. Ejected into prostatic urethra by peristalsis of prostate wallc. Slightly acidicd. Seminalplasmin: may help prevent UTIs in males vi. Bulbourethral glands 1. Aka. Cowpers glands2. Compound, tubular mucous glanda. Empties into spongy urethra3. Found at base of penisa. Duct of each gland travels next to the penile urethra and empties into the urethral lumen4. Thick, alkaline mucus secreted to help neutralize urinary acids in urethra a. Lubricates the glans of penis g. Semen i. 2-5 mL released in a typical ejaculationii. Abnormally low volume may indicate problems with prostate gland or seminal glandsiii. Sperm count1. Usually 20-100 million spermatozoa/mL of ejaculate2. In order to determine this, semen is collected after 36 hours of sexual abstinence iv. Ejaculate1. Contains spermatozoa, seminal fluid, and enzymesa. Enzymes include:i. Proteaseii. Seminalplasminiii. Prostatic enzyme causes semen to coagulate by converting fibrinogen to fibrin a few minutes after ejaculationiv. Fibrinolysin after about half hour, it liquefies the clotted semen h. External genitalia i. Penis: tubular organ in which distal portion of urethra passes 1. Conducts urine to exterior2. Introduces semen into females vagina3. Root: fixed portion, attaches penis to body walla. This attachment occurs in the urogenital triangle, under the public symphysis 4. Body or shaft: tubular, movable portion of the penis a. Composed of 3 cylinder columns of erectile tissue5. Glans: expanded distal end of penis that surrounds the external urethral orifice 6. Dermis of penisa. has layer of smooth muscle which is a continuation of dartos muscleb. underlying areolar tissue allows the skin to move freelyc. subcutaneous layer contains superficial veins, arteries and lymphatic vessels 7. Prepuce (foreskin)a. Fold of skin surrounding tip of penis, attaches to neck and continues over the glans8. Erectile tissue a. Located in body of penis b. Has network of
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