Download The Reproductive System

The Reproductive System
The Male
- The scrotum, which contains the testis, is a few degrees cooler than that of the
abdominal cavity because sperm cannot develop at body temperature
- The vas deferens carries sperm from the testes to the urethra. A vasectomy can be
done to prevent this from happening. The ejaculatory duct regulates the movement of
semen into the urethra, which is also where urine comes out
- A sphincter (circular muscle) regulates the movement of urine from the bladder. At any
given time, the urethra conducts either urine or sperm, but never both at the same time
- During sexual excitement, the erectile tissue in the penis fills up with blood. The
parasympathetic nerve is stimulated, causing arteries leading to the penis to dilate,
increasing blood flow. As blood moves into the penis, the sinuses swell, compressing the
veins that carry blood away from the penis
- Sperm cells have very little cytoplasm. This is good for movement, but it also makes the
sperm have limited energy. Sertoli Cells nourish the developing sperm.
- At the tip of the sperm, there is an acrosome which is filled with special enzymes that
dissolve the outer coating surrounding the egg, allowing it in
- Inside the testis, there are seminiferous tubules which are lined with sperm-producing
cells called spermatogonia. During meiosis, spermatogonia divide into spermatocytes.
Sperm cells then mature in the epididymis (attached to outer edge of the testis)
-
Fluid is secreted by 3 glands along the vas deferens and the urethra
1. Seminal vesicle
2. Prostate gland
3. Couper’s gland (bulbourethral)
1. Seminal Vesicle – secretes fluid that contains fructose (source of energy for sperm) and
contains prostaglandins facilitating the relaxation of the muscle walls that delineate blood vessels,
effectively dilating them (act as chemical signal in the female system)
2. Prostate Gland – secretes an alkaline buffer that protects sperm against the vagina’s
acidity
3. Couper’s Gland – secretes mucus-rich fluids before ejaculation, which protect sperm from
acidity in urethra because of urine, and assist in sperm movement
Male Hormones
- Androsterone and testosterone are produced in the interstitial cells of the testes.
- Testosterone – stimulates spermatogenesis (maturation of sperm cells)
- also influences development secondary sex characteristics (facial and body hair),
growth of larynx, strengthening of muscles
- used in production of anabolic steroids
-
The hypothalamus and pituitary gland control the production of testosterone, other
hormones, and sperm
Gonadotropic hormones – regulate function of testes
FSH (follicle stimulating hormone) – stimulates production of sperm cells
LH (luteinizing hormone) – promotes production of testosterone by the interstitial cells
(cells in the testes)
GnRH (gonadotropin releasing hormone) – activates pituitary gland to secrete and release
FSH and LH
Vasectomy Procedure
Sperm
The Female
Zygote – fertilized egg
Blastocept – when the fertilized egg reaches the uterus (6 days after fertilization) it has been
transformed into a cell mass
Implantation – when the blastocept becomes attached to the wall of the endometrium
HCG – a hormone (human chorionic gonadotropic hormone) which maintains the corpus luteum
(produces progesterone estrogen which maintain the endometrium) for the 1st 3 months of
pregnancy
- identifiable in urine of pregnant women
Chorion – outer membrane of blastocept, produces HCG
Amnion – inner membrane of blastocyst, evolves into fluid-filled sac that insulates the embryo
Placenta – made up of cells of the fetus and cells of the endometrium
Chorionic villi – projections of the placenta which ensure that many blood capillaries of the
mother are exposed to a large number of blood capillaries of the fetus
Allantois – a membrane that provides blood vessels in the placenta
- does not envelop the fetus like the chorion and amnion does
Umbilical cord – connects the embryo with the
placenta
1st Trimester – from fertilization to the end of
the 3rd month
- 3 germ layers form (ectoderm,
mesoderm, and endoderm)
- heart has formed, limb buds have
developed
2nd Trimester – from beginning of 4th month to
the end of the 6th month
- all organs are formed
- eyelids and elelashes form
3rd Trimester – from the beginning of the 7th
month to birth
– baby grows rapidly
– organs become more developed
Female Hormones
Relaxin – hormone produced by the placenta prior to labor
- causes ligaments within the pelvis to loosen, providing a more flexible passage-way for
the baby during delivery
Oxytocin – a hormone from the posterior pituitary gland, causes strong uterine contractions
Lactation – elevated levels of estrogen and
progesterone prepare the breasts for milk
production
Prolactin – hormone produced by the pituitary gland,
responsible for stimulating glands within the breast
to begin producing fluids
In Vitro Fertilization
– the egg is fertilized outside of the body
- Laparoscope – device inserted into the woman’s
abdomen, enables the physician to locate the ovary:
allows the extraction of eggs form the ovary
Diabetes Mellitus
Diabetes mellitus is a chronic disease caused by inherited and/or acquired deficiency in
production of insulin by the pancreas, or by the ineffectiveness of the insulin produced. Such a
deficiency results in increased concentrations of glucose in the blood, which in turn damage
many of the body’s systems, in particular the blood vessels and nerves.
There are two principle forms of diabetes:
- Type 1 diabetes (formerly known as insulin-dependent) in which the pancreas fails to
produce the insulin, which is essential for survival. This form develops most frequently in
children and adolescents, but is being increasingly noted later in life
- Type 2 diabetes (formerly named non-insulin-dependent) results from the body’s inability
to respod properly to the action of insulin produced by the pancreas. Thype 2 diabetes is
much more common and accounts for around 90% of al diabetes cases worldwide. It
occurs most frequently in adults, but is being noted increasingly in adolescents as well.
Certain genetic markers have ben shown to increase to risk of developing Type 1 diabetes. Type
2 diabetes is strongly familial, but it is only recently that some genes have been onsistenly
associated with increased risk for Type 2 diabetes in certain populations. Both types of
diabetes are complex diseases caused by mutations in more than one gene, as well as by
environmental factors.
Diabetes in pregnancy may give rise to several adverse outcomes, including congenital
malformations, increased birth weight and an elevated risk of perinatal mortality. Strict
metabolic control may reduce these risks to the level of those of non-diabetic expectant
mothers.
Impaired glucose tolerance (IGT) and impaired fasting glycaemia (IFG) refer to levels of blood
glucose concentration above the normal range, but below those which are diagnostic for
diabetes. Subjects with IGT and/or IFG are at substantially higher risk of developing diabetes
and cardiovascular disease tan those with normal glucose tolerance. The benefits of clinical
intervention in subjects with moderate glucose intolerance is a topic of much current interest
Symptoms – The symptoms of diabetes may be pronounced, subdued, or even absent
- In Type 1 diabetes, the classic symptoms are excessive secretion of urine (polyuria),
thirst (polydipsia), weight loss and tiredness
- These symptoms may be less marked in Type 2 diabetes. In this form, it can also happen
that no early symptoms appear and the disease is only diagnosed several years after its
onset, when complications are already present.
Sexual Versus Asexual Reproduction
Asexual reproduction does not involve sex cells or gametes (produced through meiosis). Rather,
it is reproduction by mitosis allowing a new, genetically identical individual to be produced. Both
methods of reproduction have advantages and disadvantages. Sexual reproduction allows
genetic variation and allows the development of a population that is specifically adapted to its
surrounding (and is therefore more likely to survive). However, when a very desirable
combination of traits is found, sexual reproduction risks losing them in the randomness of the
process. Asexual reproduction does not allow genetic variation, but guarantees reproduction (no
dependence on others). It rapidly increases numbers of an organism and keeps its desired
combination of traits. Many plants reproduce use a combination of sexual and asexual
reproduction to get the benefits of both methods.
The earthworm is a hermaphrodite. A hermaphrodite is an animal that has both the male and
female reproductive organs. During mating, both individuals behave as both sexes. Each
individual both receives and donates sperm. This greatly increases the number of potential
mates by allowing a worm to make with any other worm in the population. Then the worms expel
the fertilized eggs into the ground, with a protective membrane surrounding them.