Introduction
The organs in the body which synthesize and secrets substances (or hormones) that do a specific task in the body are called glands. These are essential organs present throughout the body.
Mammals have a wide variety of skin glands which are the variation of two major groups:
- Sudoriferous (Sweat) glands
- Sebaceous (oil) glands
1. Sudoriferous (Sweat) glands
They are long tubular structures of cuboidal cells, the secretory portions of which are coiled and embedded in the dermis. From the glands, convoluted ducts run the surface of the skin through which sweat is discharged.
The evaporation of sweat from the body produces a cooling effect which is the temperature regulation strategy of the body. Moreover, it also secretes salt, urea, and other waste products.
Sweat glands are mainly present in mammals but are absent in pangolins, echidnas, whales, dolphins, porpoises, etc. In mammals having fur, these glands are present in parts with the least fur such as soles of feet as in cats and lips as in rabbits.
Lesser the number of hairs, the greater the number of sweat glands. Man has a larger number of sweat glands. This is due to the fact that the human body is covered with fewer hairs.
2. Sebaceous (Oil) glands
Oil glands secrete oily mixture known as sebum into the hair follicles. The sebum is a mixture of fatty acids and cellular debris. It lubricates the hairs, prevents from desiccation, and acts as a barrier against moisture entering the body.
These are absent from the palms, soles but are present on other hairless areas such as lips.
Following are the modified sebaceous glands:
Ceruminous Glands:
These are modified sebaceous glands present in the ear canals of mammals. They secrete waxy material called cerumen. The hair and wax trap insects to prevent debris, dust, microorganisms, and other harmful particles from entering the inner ear.
Tarsal Glands:
The modified sebaceous glands are embedded in the dense connective tissue plate called tarsus are present in each eyelid. They secrete oil into the conjunctiva of the eyeball. It prevents eyes from the evaporation of tear film.
Scent Glands:
These are the modified sebaceous as well as Sudoriferous glands. There are a variety of scent glands but mostly are pheromonal and defensive.
Pheromones:
Substances secreted in small amounts cause special reproductive, developmental, and behavioral responses.
Skunks have glands to produce pungent odor which drive away their enemies. The scent glands produce a variety of odors in mammals. In zoos, the bad-smelling is not due to unhygienic conditions but due to these glands.
Example: Male musk has musk gland to signal the sex.
Temporal Glands
These are the glands present in elephants. During the breeding season, it swells and secretes a sticky brown fluid. At this time, elephants are aggressive and dangerous.
Mammary Glands
These are modified sebaceous glands which develop in both sexes. The location and number of mammary glands vary in different species. These glands are present in almost all mammals such as cats, dogs, pigs, rodents, monkeys, men, apes, etc.
But they are absent in some mammals, Monotremes (spiny ant-eater, Duck-billed platypus) have mammary glands that lack teats. But both the male and the female have modified sweat glands that produce nutritious secretions. So young ones lick up this secretion from the tuft of hair.