22 Reproductive

Ch. 22 Reproductive Systems

Specialized jobs of the Male Reproductive system:- produce and maintain the male sex cells- to transport these cells to the female- to secrete male sex hormones

Primary sex organs (gonads) are the 2 testes- sperm cells are formed here- male sex hormones are formed

Accessory sex organs- are the other structures of the male repro. system- internal reproductive organs- external reproductive organs

Male Reproductive Organs

Male Reproductive Organs

posterior view

Descent of Testes

Usually a month or two before birth, these organs descend to the lower abdominal cavity and pass through the abdominal wall into the scrotum.

Gubernaculum

Structure of the Testis

Spermatogenesis

Meiosis

• Includes two successive divisions– First meiotic division

• Separates homologous chromosomes

– Second meiotic division• Each cell emerges with one member of each

homologous pair (haploid)

Meiosis I• Prophase I

– chromosomes thicken, nulcear membrane disappears

– Homologous chromosomes pair up side by side and intertwine (synapsis)

• Metaphase I– Chromosome pairs line up midway

• Anaphase I– Homologous chromosome pairs separate (apart)

• Telophase I

Crossing Over

• mixes up traits• red is from Mom• green is from Dad

Meiosis II• Very similar to a mitotic division

• Prophase II

• Metaphase II

• Anaphase II

• Telophase II– Potential to produce 4 gametes

• Males 4 sperm cells

• Females 1 large cell; 3 polar bodies cast away (849)

Oogenesis

Crossing Over

• the genetic information in sperm cells and egg cells varies from cell to cell

Structure of a Sperm Cell

Male Internal Accessory Organs

• epididymis• vas deferens• seminal vesicle• prostate gland• bulbourethral glands

Epididymis

• Promotes maturation of sperm cells• Stores sperm until ready to exit the body

Vas Deferens• muscular tube• about 45 cm• dilates into the ampulla near termination• extends from epididymis to ejaculatory duct

Seminal Vesicle

• secretes fructose (energy for sperm)• secretes prostaglandins (for female contractions)• contents empty into ejaculatory duct

Prostate Gland• surrounds beginning of urethra, just inferior to the urinary bladder• secretes an alkaline fluid that neutralizes the sperm-cell containing fluid• secretion enhances motility of sperm cells•neutralizes the acidic secretions of the vagina• If swollen puts pressure on urethra, making it hard for urine or sperm to exit

Bulbourethral Gland

• AKA Cowper’s gland •inferior to the prostate gland• secrete mucouslike fluid • lubricates the end of the penis

•View Human Atlas (Prostate Cancer)

Semen

• sperm cells• secretions of seminal vesicles, prostate gland, and bulbourethral glands• slightly alkaline (7.5)• prostaglandins• nutrients• 120 million sperm cells per milliliter (release 2-5 mL)

Male External Reproductive Organs

• scrotum• penis

Scrotum

• pouch of skin and subcutaneous tissue• dartos muscle – smooth muscle in subcutaneous tissue; contracts to cause wrinkling of the scrotum; relaxes to move away from the body

• **Sperm are housed away from the body because they must be 5 ºF cooler in order to survive**

• medial septum divides scrotum into two chambers• each chamber houses a testis and epididymis

Penis

- 3 columns of erectile tissue- Pair of corpora

cavernosa- Single corpus

spongiosum- Urethra passes

through this tissue

Hormonal Control of MaleReproductive Functions

• Figure 22.17 hypothalamus controls maturation of sperm cells and development of male secondary sex characteristics• negative feedback controls concentration of testosterone

Hormonal Control of MaleReproductive Functions

• hypothalamus controls maturation of sperm cells and development of male secondary sex characteristics• negative feedback controls concentration of testosterone

Actions of Testosterone

• increased growth of body hair• sometimes decreased growth of scalp hair• enlargement of larynx and thickening of vocal cords• thickening of skin• increased muscular growth• thickening and strengthening of the bones

Organs of the Female Reproductive System

- specialized to produce and maintain female sex cells- transport these cells to the site of fertilization- to provide a favorable environment for a developing

offspring- to move the offspring to the outside- to produce female sex hormones

- Primary sex organs (ovaries)- Produce eggs and sex hormones

- Accessory sex organs- Internal and external reproductive organs

Transverse Section of Female Pelvic Cavity

Ovaries

• Several ligaments help hold each ovary in position

• Descend like the male testes do

• Of the several million oocytes formed, only a million or so remain at birth and around 400,000 at puberty

• Fewer than 400-500 will be released

Ovary Attachments

Oogenesis

Oogenesis• Distribution of the cytoplasm is unequal

– Secondary oocyte– First polar body

• If fertilized, the oocyte divides unequally to produce a tiny second polar body and a large fertilized egg cell or zygote

• Will develop into an embryo (2nd – 8th weeks)

• Polar bodies allow for production of an egg cell that has a massive amount of cytoplasm and organelles required to get through first few cell divisions

Ovulation

- Release of an egg cell- Usually propelled to

the opening of a nearby uterine tube

- If it is not fertilized it degenerates

- Watch Human Atlas Ectopic Pregnancy

Female Internal Accessory Organs

• uterine (fallopian) tubes• uterus• vagina

Uterine (Fallopian) Tubes

• Place egg should be fertilized!

• Near each ovary, a uterine tube expands to form a funnel-shaped infundibulum– Partially encircles the ovary medially– Infundibulum bears a number of irregular,

branched extension called fimbriae– Generally does not touch the ovary

• One of the larger ovarian fimbria connects directly

Uterus• Receives the embryo that develops from an egg cell

that has been fertilized and sustains its development

• Hollow muscular organ, like an inverted pear

• Usually bent forward over the urinary bladder

• Upper 2/3 is the body

• Lower 1/3 is the cervix

• Layers of the uterine wall– Endometrium- inner lining– Myometrium- muscular layer; smooth muscle– Perimetrium- outer layer

Uterine Wall

Vagina

• Fibromuscular tube about 9 cm long that extends from the uterus to the outside

• Open channel for offspring during birth

• Posterior to the urinary bladder and urethra & anterior to the rectum

Hormonal Control of FemaleReproductive Functions

• Figure 22.31 estrogens inhibit LH and FSH during most of the reproductive cycle

Effects of Estrogens

• development of breasts and ductile system of the mammary glands• increased adipose tissue in breasts, thighs, and buttocks• increases vascularization of skin

Mammary Glands

Surgical Methods of Birth Control

Sexually Transmitted Diseases

• silent infections• most are bacterial and can be cured• herpes, warts, and AIDS are viral and cannot be cured• many cause infertility• AIDS causes death• symptoms of STDs include

• burning sensation during urination• pain in lower abdomen• fever or swollen glands• discharge from vagina or penis• pain, itch, or inflammation in genital or anal area• sores, blisters, bumps or rashes• itchy runny eyes

Terms to Know on Page 868• Amenorrhea

• Endometritis (endometriosis)

• Epididymitis

• Hysterectomy

• Mastitis

• Ovariectomy

• Orchiectomy

• Prostatectomy

- itis- means inflamed- ectomy- removal of an

organ surgically