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Human Reproduction. Male Reproductive Structures. During puberty the males primary sexual characteristics mature and enable a male to reproduce – i.e. he does not produce sperm or the capability to reproduce prior to puberty. . Male Reproductive Structures.
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Male Reproductive Structures • During puberty the males primary sexual characteristics mature and enable a male to reproduce – i.e. he does not produce sperm or the capability to reproduce prior to puberty.
Male Reproductive Structures • There are two testes that are in a protective sac called the scrotum. • The testes produce and nourish the developing sperm. • Each testis contains the seminiferous tubules, which contain the sperm cells. • Sitting above that is the epididymis, this is where the mature sperm is stored.
Male Reproductive Structures • Attached to the epididymis is the the vas deferens tube. This tube carries the sperm up to the urethra. • When males undergo a vasectomy, it is the vas deferens tube that gets cut. This procedure is non-reversible. • The urethra is a little tube inside the male penis, this tube transports both the sperm and urine from the male body. • NOTE the urine and sperm cannot travel through the urethra at the same time – it is impossible.
The Human Sperm • The structure of a human male sperm:
The Human Sperm • At the head of the sperm is the nucleus that contains 23 chromosomes. • The capsule has chemicals in it that allows the sperm cell to enter the egg. • The mitochondria is what gives the sperm energy to move. • The flagellum is a whip-like tail that helps propel the sperm.
The Human Sperm • Sperm cells have a short life cycle. It takes 65 – 75 days for a sperm to be created inside the male testicles. • Males can produce up to 200 – 300 million sperms each day. Sperm that is not released die and within a few days are broken down. • Only a mature sperm cell can make its way to the egg, and the older a male gets the less mature sperm cells they can create (and we are talking really old peeps)
The Human Sperm • In order for the sperm to make its journey from the male body to the female egg, it needs to get nutrients from the male body. • The seminal vesicles, prostate gland, and Cowper’s gland are accessory glands that release seminal fluid. • Seminal fluid provides • sugar for energy (the mitochondria absorbs this); • it also protects the sperm from the acidic female reproductive tract; and • Provides the fluid for the sperm to swim/move in • The sperm and seminal fluid together make up semen
Female Sexual Characteristics • Female puberty usually begins around the age of 10 – 12 (so on average about a 1 – 2 before males begin puberty). • Unlike a male – who does not start to produce his sperm until puberty – females have all their sex cells at birth. • A female can be born with approximately two million eggs, but will have only about 400,000 at puberty. • Once sexual maturity is reached during puberty a single egg matures and will be released each month.
Female Sexual Characteristics • The primary female reproductive organ is the ovary, this is where the egg cells mature and are released from. • Females have two ovaries located in the lower portion of the abdominal cavity one on either side of their sex organ. • Inside the ovaries are follicles, each follicle contains a single immature egg. • Females are able to produce their own hormones –estrogen and progesterone – in the ovaries.
Path of the Egg • A women goes through a menstrual cycle, each cycle is typically 28 days. • The length of a women’s cycle can change the older they get. It can also change if one women lives with other females (for example in a dorm). This is known as the McClintock synchronization theory. • When a female reaches the age of 40 she goes through menopause and this is when she tends to stop producing mature eggs.
Path of the Egg • After an egg is developed and mature it is released from the ovary into the fallopian tube – usually one egg from one ovary and the next cycle it will release an egg from the other ovary. • The fallopian tube is a tube that allows the egg to get from the ovaries to the uterus. • The lining of the uterus is called the endometrium, it is filled with rich nutrients, blood vessels and mucus that provides nourishment for the embryo.
Path of the Egg • The cervix is a muscle between the vagina and the uterus – it is clamped relatively shut and only starts to open during child birth. • This helps to ensure that the egg stays in the uterus until full maturation when child birth begins. • The vagina has three main functions • Receives the male penis and sperm during sexual intercourse; • Is the birth canal during delivery of an offspring; and • To void the bladder
Path of the Egg • If no sperm is found in the fallopian tube to fertilize the egg, the egg will make its way to the uterus and expel through the vagina. • If fertilization does occur, it must happen within 24 hours of ovulation (when the egg is released) or the egg degenerates. • The egg moves to the uterus, and once the uterus realizes that the egg is not fertilized, it then sheds the endometrium and starts to prepare for the next cycle.
Pregnancy • If the egg is fertilizedin the fallopian tube, the egg and sperm fuse together to produce a zygote. • After fertilization, the mass of cells created in the zygote become an embryo. • The Embryo reaches the uterus where it will implant into the endometrium. • During pregnancy the menstrual cycle stops completely while the mother-to-be awaits for the birth of her baby. • Upon the birth of an offspring, females produce a hormone called prolactin. It causes milk to be produced to feed the baby.
