Unit Four Human Populations: Reproduction and Ecology

In this unit we learned about the reproductive system and ecology. Some of the topics I will be discussing are:
*the reproductive system
*fetal development and birth
*the human life cycle
*meiosis
*human history long term
*human ecology - physical and biological landscape
*natural selection

The Reproductive System









The male reproductive system consists of the:

Testes - The testes are two egg shaped organs located in the scrotum. They produce sperm and testosterone.

Epididymides _ A long narrow coiled tube located in the testes that stores and transports sperm to the vas deferens.

Vasa Deferentia - The main duct that semen is carried in from the epididymis to the ejaculatory duct.

Seminal Vesicles - About 2 inches long located behind the bladder and about the prostate, contributes fluid to semen.

Prostate Gland - Produces part of the semen, surrounds the ejaculatory ducts at the base of the urethra.

Urethra _ Carries semen and urind outside of the penis.
Bulbourethral Glands - Also known as cowpers gland, pea shaped located beneath the prostate gland. Adds fluid to semen during ejaculation.

Penis - Male sexual and reproductive organ consisting of the glans (head) and shaft (body). Contains many nerve endings that make it sensitive to touch, pressure and temperature.









The female reproductive system consists of:

Fallopian Tubes or Oviducts - Extend from the uterus to the ovaries, although they are not attached to the ovaries. Cilia in the oviduct draws the egg in. The trip down the fallopian tube takes about a week.

Ovary - Also called eggs is the female gonad that produces eggs and female sex hormones.

Uterus - Or womb is an very small organ located in the female pelvis. This is where the fetus develops.

Endometrium - Mucous membrane lining the inside of the uterus. Has a rich cappilary supply to bring food to an embryo that might implant there.

Cervix - Narrow end of the vagina that projects into the vagina. Secretes mucous that varies during different types of the menstrual cycle.

Bladder - Hollow, muscular organ that sits on the pelvic floor. Collects urine excreted by the kidneys.

Urethra - Tube that connects the bladder to the outside of the body. The urethral sphincter is a smooth muscle that allows voluntary control over urination.

Clitoris - Located at the anterior end of the labia, under the pubic bone. Contains erectile tissue and many nerve endings.

Labia majoria - The larger outside pair of labia (lips).

Labia minora - The smaller inner pair of labia (lips).

Vagina - Organ that leads from the uterus to the vestibule and serves as the birth canal and organ of sexual intercourse.

Fetal Development and Birth

8 week old embryo

First Trimester -

Conception occurs at the moment the sperm penetrates the egg. The fertilized egg is called the zygote until it reaches the uterus in approximately 3- 4 days. The embryo attaches to the uterus wall and the placenta starts to form. The most crucial time during the pregnancy. The embryo goes through many rapid changes during the first trimester. Everything from limbs to vital organs are formed during this time.

Second Trimester -



The brain is fully developed now. The fetus can suck, swallow, and make irregulat breathing sounds. Fetal skin is transparent, muscle tissue is lengthening and bones are becoming harder. Liver and organs are producing appropriate fluids. Fetus making active movements. The baby is covered in lanugo (fine hair).

Third Trimester -

Fetus covered in vernix a waxy substance secreted by the sebaceous glands to protect the fetus's skin from dehydration in the womb.

Rapid brain development occurs during this month. The nervous system is able to control some bodily functions. Rapid increase in the fetus's body fat. Footprints and fingerprints form during this time. Fetus sleeps 90-95% of the time. The closer you get to 40th week of pregnancy the higher the fetus's survival rate is.

Birth



Signs of labor may include: a bloody show (mucous plug), contractions, leaking amniotic fluid due to water breaking.

Contractions push the fetus downward and the cervix dilates and stretches.

There are 3 stages of labor.

During the first stage of labor the contraction cause the cervical canal to slowly disappear as the lower part of the uterus is pulled up toward the baby's head. This is called effacement. As the babies head pushes against the cervix it causes it to dilated. The first stage is complete once the cervix is dilated to 10 cm.

During the second stage contractions are closer together, usually occuring 1-2 minutes apart. The mother will feel the urge to push as the baby's head works its way into the vagina. The the baby's head reaches the exterior it turns to that that back of the head is facing up. An episiotomy may be performed at this time to enlarge the opening. Once the baby is fully delivered and breathing normally the umbilical cord is cut.

Stage three of the labor is when the placenta or afterbirth is delivered.