Animal Tissue and Anatomy

Cells of simple squamous epithelium are flat with flattened/rounded nucleus. It is also called pavement epithelium due to its tile-like appearance.

Ciliated columnar epithelium moves mucus and other substances via cilia and is found in the upper respiratory tract and the fallopian tubes.

The epithelia of body cavities that are connected to the external environment protect themselves by secreting large amount of mucus by numerous mucus-secreting cells.

Alveoli are tiny ends of the alveolar ducts. These tiny air sacs function to exchange oxygen and carbon dioxide in the blood. Certain respiratory diseases cause a thickening of the alveoli walls, which restricts movement, causing breathing difficulties.

The lowest portion is called the laryngopharynx, which extends downward and becomes continuous with the esophagus and larynx. Both the oropharynx and laryngopharynx are digestive and respiratory pathways.

The respiratory tract (or system) is a complex arrangement of organs and tissues. Its main functions are taking in oxygen and getting rid of carbon dioxide. The respiratory tract can be separated into two parts: (a) the proximal-conducting, non-respiratory airways that include the nose, pharynx, larynx, trachea, bronchi, and non-alveolar bronchioles, and (b) the distal respiratory region (i.e., respiratory bronchioles, alveolar ducts, and alveoli).

Nose is the first potential target for inhaled substances, except when one breathes through the mouth. Nose is important in odour detection. Interior parts of the nose warm, moisten, and filter air. This helps to protect the lungs from harm. Some inhaled material is trapped in the nasal cavity. The trapped material can, however, be transported from there to the throat, where it is swallowed. Nose blowing can also remove deposited material from the nose.

Elastic cartilage or yellow cartilage is a type of cartilage present in the outer ear, larynx, and epiglottis. It contains elastic fiber networks and collagen fibers. The principal protein is elastin.

Lungs are cone-shaped and extend from the collar bone to the surface of the diaphragm. The mid-line of each lung contains a region known as the hilus, the area through which blood and lymphatic vessels, nerves and primary bronchi enter and leave. Each lung is divided into lobes, three in the right lung and two in the left, within which there are smaller divisions known as lobules.

The sinuses are hollow areas or cavities in the bones of the skull that are lined with mucous membranes and that open into the nasal cavity. The sinuses provide resonance for the voice. When the sinuses are inflammed and filled with mucus the voice has a different quality, often referred to as nasal in character.

Moving further down the respiratory tract, we reach the larynx, or voice box, which contains the vocal cords. The voice is produced by controlled vibrations of the vocal cords as air is pushed out of the lungs and through the larynx.

It is made up of more than one layer of cells and has a limited role in secretion and absorption. Their main function is to provide protection against stress. They cover dry surface of skin, moist surface of buccal cavity, pharynx and inner lining of salivary glands.

 The part of fallopian tube closest to the ovary is infundibulum.

Abducens is a motor nerve whereas Optic is a sensory nerve.

Optic, oculomotor, trochlear and abducens nerves innervate eye.