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UNCW BIO 241 - Reproduction and the Role of the Male

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BIO 241 1st Edition Lecture 29 Test 6Outline of Current Lecture II. Overview of reproductionIII. Male reproductive system -- scrotumIV. TestisV. SpermatogenesisVI. SpermiogenesisVII. Hormonal control of male reproductionVIII. The spermatic ductsIX. UrethraX. Accessory sex glandsCurrent LectureII. Mitosis is used for growth and repair by making identical daughter cells. Meiosis is used to make gametes - sperm and eggs. The essence of reproduction is biparental (male and female). Therefore, fertilization produces a zygote, which has its own genetics. The role of the male is to produce sperm and introduce sperm into the female body. The role of the female produce ova (eggs), receive sperm and provide for union of the gametes, harbor an embryo/fetus and give birth, and nourish offspring. The primary sex organs (used directly for reproduction) are the gonads – ovaries and testes. Secondary sex organs (everything else related to reproduction) such as breasts.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. The main reason why the testes are located outside of the body is for temperature regulation. Sperm production is optimal between 3-5 degrees cooler than body temperature. This is why they raise closer to the body when cold, and lower when warm. The testes have to descend out of the body and this occurs through the inguinal canal. Following this route, the spermatic cord consists of ductus deferens, testicular artery, pampiniform plexus, and autonomic nerves. Dartos’ fascia (muscle) is located just under the outer epithelium and contracts the skin of the scrotum to tuck them closer under the body. The cremaster muscle encloses the spermatic cord. This muscle also elevates the testes closer to the body. IV. The outer layer of the testis is the tunica vaginalis and the inner is tunica albuginea. Extensions of the tunica albuginea create 250-300 lobules that each contain seminiferous tubules. The germinal epithelium along with a basement membrane separate each tubule. Within the tubules, there are two cell types. The germ cells are responsible for spermatogenesis(meiosis) and sustentacular (Sertoli) cells are responsible for spermiogenesis (taking a genetically correct cell and making it mature sperm) and also secretes inhibin. Between the seminiferous tubules are interstitial cells (of Leydig) which secrete testosterone. V. Spermatogenesis begins with a spermatagonium which occur from mitosis and is 2n2c (two chromosomes and two genes on each chromosome). The primary spermatocyte is a spermatagonium that has entered meiosis and is 2n4c (two chromosomes and two chromatids so four genes). The first meiotic division occurs (reduction division) which creates 2 secondary spermatocytes (1n2c). The second meiotic division occurs which creates 4 spermatids (1n1c). This begins spermiogenesis.VI. Sertoli cells partially engulf the spermatid and provide nourishment, waste removal, and the blood-testis barrier. At anatomical maturation, sperm has a head (nucleus + acrosome [enzymesto digest a path into the egg]), midpiece (mitochondria), and tail (flagellum). It sheds most of its cytoplasm. 300 million sperm are made per day. VII.VIII. Straight tubules → Rete testis → Efferent ductules → Ductus epididymis (functional maturation, storage (40 – 60 days), and resorption if unused) → Ductus (vas) deferens (path in the body, terminate as ampulla, joins seminal vesicle duct) → Ejaculatory duct (passes into prostate gland and joins urethra)IX. The male urethra has three parts: prostatic, membranous, and spongy (penile). X. Males have accessory sex glands. One is seminal vesicles (60% of semen) that secrete fructose/other alkaline carbohydrates, prostaglandins (stimulate smooth muscle contraction in female uterus), and proseminogelin (inactive and fibrin-like). Prostate gland (30% of semen) secretes citrate (activation of mitochondria in sperm and motility), calcium, phosphate ions, clotting enzymes (proseminogelin mixes with this and leaves semen with seminogelin which coagulates and makes semen less watery), and serine protease (dissolve coagulated semen). Bulbourethral glands are located at the pelvic diaphragm and are closest to the exit. They secrete pre-ejaculatory fluid which contains mucus and acid buffers (to neutralize the acidity from


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UNCW BIO 241 - Reproduction and the Role of the Male

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