Female and Male Reproductive Systems: Anatomy and Functions
Female:
1. Ovaries: Produce ova and female hormones (oestrogen), every 28 days an ovum is released by one of the ovaries
2. Oviducts: the funnel at the front receives the ovum, and it contains cilia to push this ovum into the uterus, fertilization occurs in the oviduct.
3. Uterus: This is where the embryo is developed (if fertilization occurs), contracts during birth to push out fetus
4. Cervix: secretes mucus to help sperm swim
5. Vagina: the organ where copulation takes place, and it is folded to allow expansion during birth. It secretes mucus to allow movement of the male organ during copulation. It secretes acid to kill bacteria and other microorganisms.
Male:
1. Testis: Produce sperms, and the male sex hormone (testosterone)
2. Scrotum: it is used to hold the testes outside the body, for a lower temperature, because higher temperatures affect sperm production
3. Sperm duct: transports sperm from the production site to the urethra, contracts in a process like peristalsis to help in ejaculation
4. Urethra: allows the passage of urine and semen, also contacts to help in ejaculation.
5. Prostate gland: secretes seminal fluid, which mixes with sperms to make semen, the seminal fluid consists of mucus (to help swimming), sugars (to provide energy for sperms), alkaline materials (to neutralize the acidic conditions of the urethra (due to remains of urine))
6. Penis: this is the organ of copulation. It contains erectile tissue, which contains blood cavities, which get filled up due to stimulation, making the penis erect for copulation.
Sperms are mobile, ejaculated in large groups, and much smaller than eggs. Eggs are immobile, released once every 28 days, and much larger than sperms.
Menstrual Cycle
First, the uterus lining builds up (due to oestrogen), this oestrogen also stimulates FSH production, which prevents further ova being produced. LH is then produced, causing the ova to be popped into the oviduct. It also causes the forming of a “yellow body”. This yellow body secretes progesterone, which thickens the lining of the uterus and maintains it. Two weeks after ovulation, the uterus lining breaks down and menstruation occurs. The cycle is then repeated.
Intercourse
First, the penis becomes erect due to stimulation. This erect penis is then inserted into the vagina, and is moved, getting stimulated, and semen is ejaculated. The sperms then swim using their tails towards the ovum. Many sperms reach the egg, and start producing enzymes to digest its way into the egg. The sperm leaves its tail outside, and has its nucleus fuse with that of the egg. This is called the zygote, which further divides, without increasing in total size, forming a ball of cells which gets implanted in the wall of the uterus.
Fetus formation
After the ball of cells is implanted in the uterus lining, it starts to grow in size as well as multiply. This embryo keeps growing, and, after about 8 weeks, when all its organs are formed, it is called a fetus. As the embryo is developing, the uterus enlarges to accommodate it. The embryo becomes enclosed in the amnion sac (which contains amniotic fluid), which protects it from damage and prevents unequal pressures on the embryo. The embryo and uterus both grow villi, and where these villi are close together is known as the placenta.
The placenta prevents high pressure blood from reaching the fetus, and prevents bacteria (not viruses) from passing through. If the blood groups of the mother and fetus are different, it prevents their mixing and coagulation. It also allows the exchange of gases between the fetus and mother (O2 from mother’s blood goes in; CO2 from fetus’s blood goes out). it also allows nutrition to reach the fetus (glucose and amino acids) and removes waste from the fetal blood, like urea. The umbilical cord connects the placenta and fetus, and the umbilical arteries carry CO2 to the placenta, and the umbilical veins carry O2 to the fetus.
Ante-natal care
1. A healthy diet, with sufficient proteins, carbohydrates, fats and minerals
2. Drugs, smoking and alcohol must be avoided
3. Gentle exercise must be done
Labor/Birth
First, the uterus contracts. The cervix then becomes soft and dilates. The amniotic sac then ruptures. The uterine contractions eventually push the baby’s head out, and the rest of the body slides out. The umbilical cord is then tied and cut. The placenta is then expelled by the uterine contractions. Cold air stimulates the baby’s lungs, causing the baby to breath.
At puberty,
the oestrogen in a female’s body starts to cause the secondary sex characteristics. These are the increased growth of the breasts, widening of the hips, growth of hair in the armpits and pubic region, and an increase in the size of the uterus and vagina. Oestrogen is produced in the ovaries.
At puberty,
the testosterone in a male’s body starts to cause the secondary sex characteristics. These are the enlargement of the testes and penis, deepening of the voice, growth of hair in the pubic region, armpits, chest, and later on, face. Testosterone is produced in the testes.
Once an ovum is released, the follicle which produced it develops into a solid body and secretes progesterone. (the body is known as the corpus luteum (“yellow body”)).
During pregnancy
the progesterone is needed in the following ways, (mostly in conjunction with oestrogen):
- Makes the uterus lining develop and secrete fluids after being primed by oestrogen
- Maintains the functions of the placenta and fights off unwanted cells near the womb that could cause damage to the placenta or fetus.
- Keeps the uterus lining in a thickened condition
- Stops the uterus making spontaneous movements
- Stimulates the growth of breast tissue
- Prevents lactation until after the birth (with oestrogen)
- Strengthens the mucus plug covering the cervix to prevent infection.
- Strengthens the pelvic walls in preparation for labour.
- Stops the uterus from contracting (thus keeping the baby where it is)