Reproductive System

Chapter 7

Reproductive System

 

Introduction 

• Reproduction is one of life. New species are produced as a result of reproduction and genetic material

• is passed from one generation to the next, i.e. from parent cells to daughter cells.   

Male Reproductive Organs 

• In the seminiferous tubules spermatozoa are situated centrally whereas spermatogonia are situated peripherally. The spermatozoa and spermatogenesis take up an intermediate position. The entire process of spermatogenesis starts and Continuus to old age the individual reach spermatogenesis spermatocytes, and spermatids and finally spermatozoon a are produced.

• The thyroid glands and gonads stimulate each other. This relation is mediated through the anterior pituitary.

• The dorsolateral masses are called the corpora cavernous penis. Inside the corpora cavernous is the midventra| mass called as the corpus spongiosum penis. This layer helps to form a spongy urethra, and is kept open for ejaculation. This layer of urethra consists of erectile tissue which contains blood sinuses. All the layers are covered by fascia and skin. Sexual stimulation may occur by visual, tactile, auditory, olfactory stimuli or even by imagination, whereupon the blood vessels that supply blood to the penis dilate. The dilation of blood vessels causes maximum blood to enter into the blood sinuses; there is expansion of spaces, and the veins get compressed. The blood that enters into sinuses is trapped. These vascular changes lead to erection. The penis comes to its original shape when the arteries are constricted and pressure on the veins is relieved. Sympathetic reflex action helps for ejaculation and the sphincter muscle at the base of the urinary bladder closes, because of which urine is not expelled out during ejaculation, and the semen does not enter the urinary bladder.

• It is a small gland present infer irony to the urinary bladder. The prostate gland secretes milky and less acidic fluid of pH 06.606.5. The fluid briefly contains ionized citric acid and is used for ATP production. Apart from this, it also contains acid phosphates, prostate-specific antigen (proteolytic enzyme), pepsinogen, amylase, lipase, and hyaluronidase.

Female Reproductive System

• The female reproductive system consists of following organs:

• 1. External genital organ: Mons pubis, Labium majus [labium majus pod Endi], Labium minus [labium minus pod Endi], clitoris and the hymen.

• 2. Internal genital organs: Vagina, uterus, ovaries and fallopian tubes. Accessory organs: Breast.

• Mammary Glands

• These are modified sweat glands, responsible for production of milk. The breast shows the presence of the nipple. Behind the nipple several small ducts known as lactiferous ducts are present. Modified sebaceous glands are present around the nipple. This space is known as the areola. The breast is supported by suspensory ligaments, which pass through the skin lying deeply inside the breast tissues. Each breast consists of 16-22 lobes. The lobes are separated by adipose tissue.

Ovary

• These are female gonads, lying in a Sheidow cavity on the lateral wall of the pelvis, one on each side of uterus. These are attached to the uterus by a broad ligament called mesovarium. The size of the ovary is variable. The length is 02.5—03.5 cm, the breadth is 02 cm and thickness is 01.25 cm.

• The Germinal Epithelium

• The surface of the ovary is covered by simple epithelial tissue. This layer is called germinal epithelium. Below the germinal epithelium, dense irregular connective tissue called as tunica albuginea is seen. Another |aye of connective tissue, lying below the tunica albuginea known as stroma is observed. The dense layer of the stroma is called as cortex and loose layer of connective is known as medulla. The cortex shows the presence of ovarian.

• It is present between the bladder and the rectum. The uterus is the site for implantation of the fertilized ovum, development of the embryo and fetus and also for menstruation. The uterus is an inverted pear-shaped organ. It is 07.5 cm long, 05 cm wide and thickness of its wall is about 02.5 cm. The uterus is divided into three parts, i.e. the fundus, body and cervix. The expanded superior part, lying above the opening of the fallopian tube is known.

• The menstrual cycle takes place in a series of events which occur at regular intervals over a period of about 28 days. There are mainly three phases.

• 1. The proliferative phase.

• 2. The secretory phase.

• 3. The menstrual phase.

• The Proliferative phase

• Under the effect of FSH, the ovarian follicle grows, and matures. At the same time, under the influence of FSH, the cells of the ovarian follicle secrete the hormone estrogen. Estrogen enters the blood to reach the endometrium where it stimulates the cells of the endometrium. As a result, the columnar cells of endometrial Iuma reproduce more rapidly to form a thicker lining of the walls of endometria Iuma. The number of glands and blood cape||arias also increase

(b) The Secretory Phase

• As soon as ovulation occurs, the walls of the ovarian follicle collapse. In this phase, FSH is withdrawn by the pituitary gland as the levels of estrogen are high in the blood. Instead, it starts to secrete the second gonadotropic hormone, the luteinizing hormone. The LH enters the blood stream reaches the ruptured follicle and influences the ruptured follicle to grow rapidly. The ruptured follicle gets filled with a yellow substance called lutein. This body is known as corpus luteum

• In the event when the ovum is fertilized, the endometrium does not break down and there is no menstrual flow. The fertilized ovum embeds itself within the endometrium and the chorionic gonadotropins are produced. This hormone keeps the corpus luteum in an intact condition so that it keeps secreting the progesterone continuously. The fertilized ovum during the first twelve weeks is called as embryo and thereafter it is known as fetus. This fetus is protected and nourished for nine months within the uterus. After the full term is reached, the baby is ready to be born.