Chapter 24: Reproductive System

Functions of Male Reproductive system

1. Production of sperm cells.
2. Sustaining and transfer of the sperm cells to the female.
3. Production of male sex hormones 

Function of Female Reproductive system

1. Production of Female sex cells.
2. Reception of sperm cells from the male.
3. Nurturing the development of baby and providing nourishment for the new individual.
4. Production of female sex hormones

Reproduction begins with a single cell.

• female produces cells, called egg cells.
• male produces cells, called sperm cells.
• when sperms joined with egg cell fertilization begins.
• fertilization starts at Fallopian tube.

Male reproductive system
















Meiosis 

• Gametes, or sex cells, have half the number of chromosomes a other cells in the body.
• Sperm cells are the male gametes and oocytes are the female gametes.
• Meiosis is a kind of cell division that produces gametes.

Chromosomes 

• The normal chromosomes number in human cells is 46
• The number is called diploid number of chromosomes.
• In the sperm cell and oocytes, the number of chromosomes is 23. This number is called haploid.

Meiotic division

• The two divisions of meiosis is called meiosis I and meiosis II.
• Before meiosis begins, all the chromosome are duplicated. 
• Each of the 46 chromosomes consist of two chromatids connected by centomere.
• The exchange of genetic material is called crossing over.

Anatomy of Male Reproductive system



Scrotum

• Scrotum- is a sac like containing the testes
• Beneath the skin layer of loose connective tissue and layer of smooth muscle, called the Dartos Muscle.
• When the scrotum is exposed to the cool temperature, the dartos muscle contract.

Testes

• Are small, ovoid organs, each about 4-5 cm long.
• They are both exocrine and endocrine.

Spermatogenesis

• is the formation of sperm cell.

Penis

• contains three columns of erectile tissue. Engorgement of this erectile tissue with blood causes the penis to enlarge and become firm, a condition called erection.

Urethra

• it is about 20 cm long and extends from the urinary bladder to the distal end of penis.
• divided into three parts: PROSTATIC URETHRA, MEMBRANOUS URETHRA, SPONGY URETHRA.
• the urethra is the passageway of both urine and male reproductive fluids. 

Prostate gland

• is about the size and shape of a walnut.
• surrounds the urethra an two ejaculatory duct at the base of the urinary bladder.

Semen

• is a mixture sperm cells and secretions from the male reproductive glands. 
• sperm cells and testicular secretions account for about 4% of semen volume.

Regulation of Sex Hormone Secretion

1. GnRH from the hypothalamus stimulates the secretion of LH and FSH from the anterior pituitary.
2. LH stimulates testosterone secretion  from the interstitial  cells.
3. FSH stimulates sustentacular celss of the seminiferous tubles to increase spermatogenesis and to secrete inhibin.
4. Testosterone has a stimulatory effect on the sustentacular cells of the seminiferous tubules, and it has a stimulatory effect on the development of sex organs and secondary sex characteristics.
5. Testosterone has a negative feedback effect in the hypothalamus and piyuitayr to reduce LH and FSH secretion.
6. Inhibin has a negative-feedback effect on the anterior pituitary to reduce FH secretion.

Female Reproductive System

The female reproductive system is designed to carry out several functions. It produces the female egg cells necessary for reproduction, called the ova or oocytes. The system is designed to transport the ova to the site of fertilization. Conception, the fertilization of an egg by a sperm, normally occurs in the fallopian tubes. The next step for the fertilized egg is to implant into the walls of the uterus, beginning the initial stages of pregnancy. If fertilization and/or implantation does not take place, the system is designed to menstruate (the monthly shedding of the uterine lining). In addition, the female reproductive system produces female sex hormones that maintain the reproductive cycle.

Parts:

• Labia majora: The labia majora enclose and protect the other external reproductive organs. Literally translated as "large lips," the labia majora are relatively large and fleshy, and are comparable to the scrotum in males. The labia majora contain sweat and oil-secreting glands. After puberty, the labia majora are covered with hair.
• Labia minora: Literally translated as "small lips," the labia minora can be very small or up to 2 inches wide. They lie just inside the labia majora, and surround the openings to the vagina (the canal that joins the lower part of the uterus to the outside of the body) and urethra (the tube that carries urine from the bladder to the outside of the body).
• Bartholin's glands: These glands are located beside the vaginal opening and produce a fluid (mucus) secretion.
• Clitoris: The two labia minora meet at the clitoris, a small, sensitive protrusion that is comparable to the penis in males. The clitoris is covered by a fold of skin, called the prepuce, which is similar to the foreskin at the end of the penis. Like the penis, the clitoris is very sensitive to stimulation and can become erect.

The internal reproductive organs in the female include:

• Vagina: The vagina is a canal that joins the cervix (the lower part of uterus) to the outside of the body. It also is known as the birth canal.
• Uterus (womb): The uterus is a hollow, pear-shaped organ that is the home to a developing fetus. The uterus is divided into two parts: the cervix, which is the lower part that opens into the vagina, and the main body of the uterus, called the corpus. The corpus can easily expand to hold a developing baby. A channel through the cervix allows sperm to enter and menstrual blood to exit.
• Ovaries: The ovaries are small, oval-shaped glands that are located on either side of the uterus. The ovaries produce eggs and hormones.
• Fallopian tubes: These are narrow tubes that are attached to the upper part of the uterus and serve as tunnels for the ova (egg cells) to travel from the ovaries to the uterus. Conception, the fertilization of an egg by a sperm, normally occurs in the fallopian tubes. The fertilized egg then moves to the uterus, where it implants into the lining of the uterine wall.

Mammary Glands (Breasts)

Functionally, the mammary glands producemilk; structurally, they are modified sweat glands. Mammary glands, which are located in the breast overlying the pectoralis majormuscles, are present in both sexes, but usually are functional only in the female. 

Externally, each breast has a raised nipple, which is surrounded by a circular pigmented area called the areola. The nipples are sensitive to touch, due to the fact that they contain smooth muscle that contracts and causes them to become erect in response to stimulation. 

Internally, the adult female breast contains 15 to 20 lobes of glandular tissue that radiate around the nipple. The lobes are separated by connective tissue and adipose tissue. The connective tissue helps support the breast. Some bands of connective tissue, called suspensory (Cooper's) ligaments, extend through the breast from the skin to the underlying muscles. The amount and distribution of the adipose tissue determines the size and shape of the breast. Each lobe consists of lobules that contain the glandular units. A lactiferous duct collects the milk from the lobules within each lobe and carries it to the nipple. Just before the nipple the lactiferous duct enlarges to form a lactiferous sinus (ampulla), which serves as a reservoir for milk. After the sinus, the duct again narrows and each duct opens independently on the surface of the nipple. 

Mammary gland function is regulated by hormones. At puberty, increasing levels of estrogen stimulate the development of glandular tissue in the female breast. Estrogen also causes the breast to increase in size through the accumulation of adipose tissue. Progesterone stimulates the development of the duct system. During pregnancy these hormones enhance further development of the mammary glands. Prolactin from the anterior pituitary stimulates the production of milk within the glandular tissue, and oxytocin causes the ejection of milk from the glands. 

The Menstrual cycle

Follicular Phase of the Menstrual Cycle

This phase starts on the first day of your period. During the follicular phase of the menstrual cycle, the following events occur:

• Two hormones, follicle stimulating hormone (FSH) and luteinizing hormone (LH) are released from the brain and travel in the blood to the ovaries.
• The hormones stimulate the growth of about 15 to 20 eggs in the ovaries each in its own "shell," called a follicle.
• These hormones (FSH and LH) also trigger an increase in the production of the female hormone estrogen.
• As estrogen levels rise, like a switch, it turns off the production of follicle-stimulating hormone. This careful balance of hormones allows the body to limit the number of follicles that mature.
• As the follicular phase progresses, one follicle in one ovary becomes dominant and continues to mature. This dominant follicle suppresses all of the other follicles in the group. As a result, they stop growing and die. The dominant follicle continues to produce estrogen.

Ovulatory Phase of the Menstrual Cycle

The ovulatory phase, or ovulation, starts about 14 days after the follicular phase started. The ovulatory phase is the midpoint of the menstrual cycle, with the next menstrual period starting about two weeks later. During this phase, the following events occur:

• The rise in estrogen from the dominant follicle triggers a surge in the amount of luteinizing hormone that is produced by the brain.
• This causes the dominant follicle to release its egg from the ovary.
• As the egg is released (a process called ovulation) it is captured by finger-like projections on the end of the fallopian tubes (fimbriae). The fimbriae sweep the egg into the tube.
• Also during this phase, there is an increase in the amount and thickness of mucous produced by the cervix (lower part of the uterus). If a woman were to have intercourse during this time, the thick mucus captures the man's sperm, nourishes it, and helps it to move towards the egg for fertilization.

Luteal Phase of the Menstrual Cycle

The luteal phase of the menstrual cycle begins right after ovulation and involves the following processes:

• Once it releases its egg, the empty follicle develops into a new structure called the corpus luteum.
• The corpus luteum secretes the hormone progesterone. Progesterone prepares the uterus for a fertilized egg to implant.
• If intercourse has taken place and a man's sperm has fertilized the egg (a process called conception), the fertilized egg (embryo) will travel through the fallopian tube to implant in the uterus. The woman is now considered pregnant.
• If the egg is not fertilized, it passes through the uterus. Not needed to support a pregnancy, the lining of the uterus breaks down and sheds, and the next menstrual period begins.