Chapter 19

THE REPRODUCTIVE SYSTEM

Introduction • Reproduction: process by which genetic material is passed from one generation to the next

Introduction (cont ’ d.) • Meiosis produces sex cells – Sperm from male and egg from female join to form zygote – Zygote develops into embryo – Embryo develops into fetus

THE MALE REPRODUCTIVE SYSTEM

Introduction • Testes: produce sperm and male sex hormones • Accessory glands: produce secretions • Accessory organs: scrotum • Penis: transporting and supporting structure

Introduction (cont ’ d.)

The Scrotum • Outpouching of abdominal wall • Supports the testes • Divided internally by a septum • Scrotal sac elevates and descends

The Testes • Tunica albuginea: capsule covering with lobules • Convoluted seminiferous tubules – Spermatogenesis

The Testes (cont ’ d.) • Spermatogenesis – Spermatogonia > primary spermatocytes > secondary spermatocytes > spermatids > spermatozoa • Sertoli cells: supply sperm cells with nutrients

The Testes (cont ’ d.) • Interstitial cells of Leydig: produce testosterone

The Testes (cont ’ d.)

The Anatomy of the Spermatozoa • Three hundred million produced daily • Anatomy – Head: contains genetic material and acrosome • Acrosome has enzymes that aid sperm in penetrating covering of ovum – Middle piece: contains mitochondria – Tail: propels sperm

The Anatomy of the Spermatozoa (cont ’ d.) • Anatomy of a sperm cell

The Functions of Testosterone • Controls development, growth, and maintenance of male sex organs • Stimulates muscle buildup and bone development • Causes sperm maturation • Causes thyroid cartilage enlargement • Produces body hair patterns

The Ducts of the System • Seminiferous tubules: transport sperm cells • Rete testis: network of ducts • Ductus epididymis: site of sperm cell maturation • Epididymis located on posterior border of testis

The Ducts of the System (cont ’ d.) • Vas deferens: straightened portion of epididymis – Enclosed in spermatic duct • Ejaculatory duct: ejects spermatozoa into urethra

The Ducts of the System (cont ’ d.) • Urethra: terminal duct – Prostatic urethra, cavernous urethra, urethral orifice

The Accessory Glands • Seminal vesicles: produce viscous part of semen • Prostate gland: produces fluid part of semen • Bulbourethral glands: produce mucus

Semen • Mixture of sperm cells and secretions • Provides energy to the sperm via fructose • Neutralizes acidity of vagina • Acts as a transport medium • Contains enzymes that activate sperm • Average volume is 2.5 to 6 mL • Seminalplasmin: destroys certain bacteria

The Penis • Delivers spermatozoa to female reproductive tract • Glans penis: end of the shaft • Prepuce: loose skin covering glans penis – Circumcision: removal of prepuce

The Penis (cont ’ d.) • Contains masses of spongy tissue with sinuses • Sinuses fill with blood resulting in erection – Compress veins so blood is retained – Help penis penetrate vagina • During ejaculation, sphincter at base of urinary bladder is closed

THE FEMALE REPRODUCTIVE SYSTEM

Introduction • Primary sex organs – Ovaries • Accessory organs – Uterine tubes, uterus, vagina, external genitalia • Accessory glands: produce mucus

Introduction (cont ’ d.)

The Ovaries • Held in position by ligaments • Covered by germinal epithelium • Tunica albuginea: cortex contains ovarian follicles • Ovarian follicles: eggs in various developmental stages • Primary follicle: contains oocyte

The Ovaries (cont ’ d.)

The Ovaries (cont ’ d.) • Oogenesis – Begins in developing female fetus (700,000 produced) – Puberty: ovarian cycle begins • Primary oocyte: first meiotic division • Mature egg: second meiotic division

The Uterine or Fallopian Tubes • Transport ova to the uterus • Infundibulum: funnel-shaped end with fimbriae • Cilia sweep an ovum into uterine tube • Egg moved by peristalsis toward uterus • Fertilization occurs in upper third of tube

The Uterus • Site of menstruation, egg implantation and labor • Pear shaped • Uterine cavity: interior of the body • Cervical canal: interior of the cervix • Uterine wall: endometrium, myometrium, perimetrium

The Menstrual Cycle • Menstrual phase – Endometrial lining shed along with blood and mucus – Ovarian follicles begin development • Preovulatory or proliferative phase – Secondary follicle matures into graafian follicle – Ovulation is rupturing of graafian follicle

The Menstrual Cycle (cont ’ d.) • Postovulatory or secretory phase – Corpus luteum develops • Secretes estrogen and progesterone – If fertilization and implantation do not occur • Corpus luteum degenerates and new cycle starts – If fertilization and implantation occur • Corpus luteum maintained for four months

Animation – Ovulation

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The Functions of Estrogen • Development of female secondary sex characteristics – Breast development, pubic hair, fat deposits, widening of the pelvic bone • Enlargement of: – Uterine tubes, uterus, vagina, external genitalia

The Vagina • Passageway for menstrual flow • Receptacle for the penis • Lower portion of birth canal • Fornix: surrounds vaginal attachment to cervix

The External Genitalia of the Female • Vulva: external genitalia • Labia: majora and minora • Clitoris: erectile tissue • Vestibule: vaginal and urethral orifices • Glands: Skene ’ s and Bartholin ’ s

The External Genitalia of the Female (cont ’ d.)

THE PERINEUM

The Perineum (cont ’ d.) • Diamond-shaped region at inferior end of trunk between buttocks and thighs • Divided into: – Anterior urogenital triangle containing external genitalia – Posterior anal triangle containing anus

THE ANATOMY AND FUNCTION OF THE MAMMARY GLANDS

The Anatomy and Function of the Mammary Glands (cont ’ d.) • Produce milk in females • Contain 15 to 20 lobes with lobules • Lobules contain milk-secreting cells • Milk is conveyed through series of tubules • Areola: circular pigmented area around nipple

The Anatomy and Function of the Mammary Glands (cont ’ d.)

PREGNANCY AND EMBRYONIC DEVELOPMENT

Pregnancy and Embryonic Development (cont ’ d.) • Egg fertilization 12-24 hours after ovulation • Zygote: fertilized egg • Moves down uterine tube into uterus – Blastula • Zygote embeds in endometrium, placenta develops

Pregnancy and Embryonic Development (cont ’ d.) • Primary germ layers – Ectoderm: skin and nervous system – Mesoderm: muscles and bones – Endoderm: linings of organs and glands • Amnion: fluid-filled sac – Attached to embryo by umbilical cord • Parturition: childbirth

Summary • Discussed the organs of the male reproductive system • Discussed the role of testosterone • Described the process of spermatogenesis • Discussed the organs of the female reproductive system

Summary (cont ’ d.) • Discussed the role of estrogen • Described the process of oogenesis • Described the phases of the menstrual cycle • Discussed pregnancy and embryonic development