Reproduction

Male Reproductive System
1. The male reproductive system performs two major functions:
 * the production of sperm cells (male gametes)
 * The deposition of these cells into the female reproductive system

2. Sperm production occurs in the testes. They are located in the scrotum where the temperature is 1-2 degrees cooler than normal body temperature. This provides an optimum temperature for sperm production and storage.

3. From the testes, sperm move to the epididymis, then through the vas deferens towards the urethra. The urethra is a tube contained within the penis. The penis is a structural adaptation for internal fertilization.

4. Glands secrete fluids, contributing to semen production. Glands include the prostate gland, seminal vesicles, and the Cowper's gland. The liquid serves as a transport medium for the sperm (an adaptation for terrestrial life).

5. In addition to producing sperm, the testes also produce the hormone testosterone. This regulates the maturation of sperm and the development of male secondary sex characteristics, such as beard development and voice pitch.

6. Male Reproductive System Diagram

Female Reproductive System
1. ﻿Ovaries are paired structures located within the lower portion of the body cavity. Ovaies produce eggs within tiny cavities called follicles. Following ovulation, the egg cell is transported through the Fallopian tube (oviduct) to the uterus. At the lower end of the uterus is the cervix. Below the cervix is the vagina, or birth canal.

2. At birth, all of the potential eggs a female will make are present in immature form. Usually, one egg is released at the time of each ovulation.

3. In addition to eggs, the ovaries also produce the hormones estrogen and progesterone. These regulate the development of secondary sex characteristics such as the development of mammary glands and the broadening of the pelvis. These hormones also have a coordinating role in the menstrual cycle.

4. Female Reproductive System Diagram

1. The menstrual cycle begins at puberty and ends at menopause. Menopause is the permanent cessation of the menstrual cycle. The duration of this cycle is approximately 28 days, but may vary considerably and may be interrupted by pregnancy, illness, and other factors.

2. The menstrual cycle consists of four stages:
 * ** Follicle Stage ** - This stage involves the maturation of the egg within the follicle (due to effect of FSH) and the secretion of the hormone estrogen by the ovaries. Estrogen helps to thicken the uterine lining.
 * ** Ovulation ** - This stage involves the release of the egg from the follicle of an ovary.
 * ** Corpus Luteum **- The corpus lutem forms from the follicle following ovulation. It secretes progesterone, which helps to thicken the uterine lining.
 * ** Menstruation ** - Menstruation is the periodic shedding of the uterine lining. It occurs when fertilizaiton doesn't take place.

3. Menstrual Cycle Diagrams



4. Menstrual Cycle Hormones
 * During the menstrual cycle, under the direction of the hypothalamus, the pituituary gland releases the hormones FSH and LH. FSH stimulates the maturation of an egg in a follicle. LH influences ovulation.
 * The ovaries secrete estrogen and progesterone, which produce changes in the uterus.
 * The hormones from the ovaries regulate the secretion of FSH and LH by the pituitary gland. This is an example of negative feedback.

Ovulation and Fertilization
1. Diagram



2. Fertilization
 * Sperm fuses with the egg in the oviduct, or Fallopian tube.
 * A ** zygote ** is the result of the fusion of gametes.

Development[[image:cleavage.jpg width="247" height="266" align="right"]]
1. The zygote mitotically divides, forming a morula (ball of cells) then a blastocyst (hollow ball of cells).

2. The blastocyst then undergoes gastrulation, forming a 3-layered embryo. Each layer differentiates into the following parts: lining of mouth, nostrils, anus, skin, sweat glands, hair, nails || Bones, muscles, blood, blood vessels, dermis, reproductive and excretory systems || Lining of digestive tract, lining of trachea, bronchi, lungs, liver, pancreas, thyroid, parathyroids, thymus, urinary bladder ||
 * Ectoderm || Mesoderm || Endoderm ||
 * Nervous system,

3. Further Development
 * Embryo - the first two months of development.
 * Fetus - from the third month until birth.
 * Once the embryo burrows into the uterine lining, a placenta must form. This structure is the connection between the mother and the fetus. It is through this structure that nutrients and oxygen diffuse from the mother's blood to the fetus' blood. Also, the placenta is the structure through which the wastes and carbon dioxide diffuse from the fetus' blood to the mother's blood.
 * The blood of the mother and fetus do not mix.

4. Fetal Development and the Placenta - the diagram