Azospermia refers to the failure of spermatogenesis. It is seen in males.

The hormone oxytocin brings about the "Let - down" reflex which is the actual ejection of milk from the alveoli of the mammary glands.

The release of ovum by the rupture of the Graafian follicle is called ovulation. It occurs during ovulatory phase of menstrual cycle.

(i) The inner glandular layer of the uterus is called endometrium.
(ii) The endometrium undergoes cyclic changes during the menstrual cycle.

The uterus or womb is a hollow, thick-walled, muscular, highly vascular and inverted pear shaped structure lying in the pelvic cavity between the urinary bladder and rectum.

(i) The epididymis is a single highly coiled tube that temporarily stores the spermatozoa and they undergo physiological maturation and acquire increased motility and fertilizing capacity.
(ii) It is found in the testis.

The accessory ducts associated with the male reproductive system include rete testis, vasa efferentia, epididymis and vas deferens.

Formation of specific tissues, organs and organ systems from three germ layers is called Organogenesis.

It is a process by which blastocyst is changed into a gastrula with three primary germ layers, namely ectoderm, endoderm and mesoderm.

(a) FSH - Follicular Stimulating Hormone
(b) LH - Lutinizing Hormone
(c) hCG - Human Chorionic Gonadotropin
(d) hPL - Human Placental Lactogen.

Spermiogenesis Spermatogenesis lt is a process of formation of sperms from immature germ cells It is a process of transformation of a non-motile spermatid into a motile
spermatozoan Number of cells increased as each spermatogonium produces four spermatids No change in number of cells as only one spermatid develops into a spermatozoa

The first cleavage in zygote produces two identical cells called blastomeres. These produce 4 cells, then 8 and so on. After 72 hours of fertilization, a loose collection of cells forms a berry shaped cluster of 16 or more cells called the morula.

Colostrum is the yellowish fluid produced from the mother's mammary glands during initial few days of location, after parturition.
Significance:
1. It has less lactose than milk and almost no fat, but it contains more proteins, vitamin A and minerals.
2. Colostrum is also rich in IgA antibodies.
3. This helps to protect the infant's digestive tract against bacterial infection.
4. Breast milk is the ideal food for infants as it contains all the constituents in suitable concentration and is easily digestable.
5. It is fully sufficient till about 6 months of age and all infants must be breast fed by the mother to ensure the growth of a healthy baby.

1. Polyspermy: An egg that has been fertilized by more than one sperm
2. When a sperm comes in contact with the zona pellucida layer of the ovum, it induces changes in the membrane of the ovum to block the entry of additional sperms.
3. The prevention of polyspermy ensures that only one sperm can fertilize a single ovum.