Category: Biology Second Paper

Gland-definition and types

The cells or groups of cells that secrete the chemical substances necessary for various biological processes in the body are called glands. The glands of the human body are of two types. Exocrine gland and Antakshara gland.
1. Exocrine Glands: The chemical substances secreted from the ducted glands are transported through the ducts to the nearby parts of the body and are active are called exocrine glands. For example – salivary gland, liver gland, pancreas etc.
2. Endocrine glands: Chemical substances secreted from ductless glands are carried through the blood or lymph to distant specific organs of the body and are active, they are called endocrine glands.

Chemical Co-ordination

Coordination between different organs and systems of the body by chemicals or hormones is called chemical coordination. There are three types of chemical combinations found in the human body. namely-
1. Endocrine Coordination: Hormones secreted from endocrine glands are transported by blood to various cells and coordinate.
2. Paracrine coordination: Chemicals secreted from cells are carried by a fluid to reach other cells and coordinate.
3. Autocrine regulation: Chemicals secreted by the same cell affect the function of that cell.

Human listening techniques

Sound waves from the external environment are received by the pinna. The received sound waves pass through the auditory meatus and strike the tympanic membrane. It vibrates the tympanic membrane. These vibrations reach the fenestra ovalis through the malleus, incus and stapes. From the fenestra ovalis passes into the perilymph. In the perilymph, the power of sound waves is increased about 20 times. It stimulates the sensory fibers of the organ of corti and generates nerve impulses. These nerve impulses reach the hearing center of the brain through the auditory nerve and the person hears sound.
At the root of the semicircular duct of the inner ear is the ampulla. Inside the ampulla are endolymph and sensory hair cells. A jelly-like cupula is attached to the follicles. The endolymph and cupula are positioned in the direction in which the human head turns or bends. Sensory cells send this message to the brain. Again, utriculus and saccule have organ called saculae. The saccule carries sensory rhombic cells. When the head tilts to one side, the otolith grains exert pressure on the hair follicles. The hair cells are stimulated and the sensation reaches the brain through the nerves. Then man can understand his relative position. Muscle contraction returns the head to its normal position. Immediately the balance of the body is maintained.

Sacculus of ear

The lower chamber of the inner ear is called sacculus. It forms a patchy tube like a snail shell. It is called cochlea. Cochlea has 3 chambers. scala vestibuli, scala media and scala tympani. The scala vestibuli is superior and filled with perilymph, the scala media is medial and filled with endolymph, and the scala tympani is inferior and filled with perilymph. The scala media consists of Ressner’s membrane above and Basil’s membrane below. Some epithelial cells above the basilar membrane transform to form the organ of Corti. Organ of Corti is a sensory organ. Organ of Corti contains 5000 sensory neurons. The place where the scala vestibula and scala tympani meet is called the helicotrima.

Utriculus of ear

The spherical chamber at the top of the inner ear is called utriculus. It consists of 3 semicircular canals. 2 vertical ducts and 1 horizontal duct. The ducts are located at right angles to each other. One end of each duct swells to form an ampulla.
The ampulla contains the sensory cells or macula. Sensory cells give rise to sensory hair cells. Sensory hair cells are embedded in otolith grains (stones). Otolith granules are covered by cupula. Utriculus maintains body balance.

Labyrinth of ear

The inner ear is located inside the auditory capsule or shrutikotar of the crown. Its main part is the membranous labyrinth. It is covered by bony labyrinth. The membranous labyrinth is filled with endolymph and the bony labyrinth with perilymph. The inner ear consists of two chambers. The human balance organ is called the vestibular apparatus. It is composed of utriculus and sacculus.

Internal Ear of Human

The inner ear is located inside the auditory capsule or shrutikotar of the crown. Its main part is the membranous labyrinth. It is covered by bony labyrinth. The membranous labyrinth is filled with endolymph and the bony labyrinth with perilymph. The inner ear consists of two chambers. The human balance organ is called the vestibular apparatus. It is composed of utriculus and sacculus.
1. Utriculus: The spherical chamber at the top of the inner ear is called utriculus. It consists of 3 semicircular canals. 2 vertical ducts and 1 horizontal duct. The ducts are located at right angles to each other. One end of each duct swells to form an ampulla.
The ampulla contains the sensory cells or macula. Sensory cells give rise to sensory hair cells. Sensory hair cells are embedded in otolith grains (stones). Otolith granules are covered by cupula. Utriculus maintains body balance.
2. Sacculus: The lower chamber of the inner ear is called sacculus. It forms a patchy tube like a snail shell. It is called cochlea. Cochlea has 3 chambers. scala vestibuli, scala media and scala tympani. The scala vestibuli is superior and filled with perilymph, the scala media is medial and filled with endolymph, and the scala tympani is inferior and filled with perilymph. The scala media consists of Ressner’s membrane above and Basil’s membrane below. Some epithelial cells above the basilar membrane transform to form the organ of Corti. Organ of Corti is a sensory organ. Organ of Corti contains 5000 sensory neurons. The place where the scala vestibula and scala tympani meet is called the helicotrima.