The Reproductive System

Chapter 19

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

Click Here to Play Ovulation Animation

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