Question

LIst the 4 types of tissues in vertebrates. Explain how the organization of the tissues at the cellular or microscopic level supports their function.

Answer 1

A tissue is a group of cells connected together that are performing similar function within an organism.

There are four basic types of tissue found in vertebrates.They are, Epithelial tissue, Muscle tissue, Connective tissue and Nervous tissue.

■ Epithelial tissue is made up of layers of tightly packed cells that line the surfaces of the body for protection, secretion, and absorption. There are two types of epithelial cells

1. Simple (made up of one layer of cells)

2. Stratified (made up of number of layers of cells)

1. Simple:

◇ Simple suamous epithelium: Made up of thin, flattened cells. Form lining of mouth, lungs and capillaries. Allow exchange of gases and materials.

◇ Simple cuboidal epithelium: Made up of cube like cells. Present in kidney tubules. Secretory and absorptive in function.

◇ Simple columnar epithelium: Made up of long column-like cells with generally nuclei at the base. Present in the lining of stomach, intestine, salivary glands. Secretory and absorptive in function.

2. Stratified epithelium: Made up of number of layers of cells. Covers the body.


■ Muscle tissue is made up of cells contain contractile filaments that move past each other and change the size of the cell. There are three types of muscle tissue: smooth muscle,skeletal muscle and cardiac muscle.

◇ Smooth Muscle

Muscle tissue in the walls of internal organs such as the stomach and intestines is smooth muscle. When smooth muscle contracts, it helps the organs carry out their functions. Contractions of smooth muscle are involuntary.

◇ Skeletal Muscle

Muscle tissue that is attached to bone is skeletal muscle. When we are blinking our eyes or running or walking , we are using skeletal muscle. Contractions of skeletal muscle are voluntary.

◇ Cardiac Muscle

Cardiac muscle is found only in the walls of the heart. When cardiac muscle contracts, the heart beats and pumps blood. Contractions of cardiac muscle are involuntary, like those of smooth muscle.

■ Connective tissue is made up of many different types of cells that are all involved in structure and support of the body. Bone, blood, fat, and cartilage are all connective tissues. Connective tissue can be densely packed together, as bone cells are, or loosely packed, as adipose tissue.

◇ Bone Tissues

Bones consist of different types of tissue, including compact bone, spongy bone, bone marrow, and periosteum.

▪Compact bone makes up the dense outer layer of bone. Compact bone is very hard and strong.

▪Spongy bone is found inside bones and is lighter and less dense than compact bone. This is because spongy bone is porous.

▪Bone marrow is a soft connective tissue that produces blood cells.

▪Periosteum is a tough, fibrous membrane that covers and protects the outer surfaces of bone.

◇ Skeleton

The human skeleton is an internal framework that, in adults, consists of 206 bones.In addition to bones, the skeleton also consists of cartilage and ligaments:

▪Cartilage is a type of dense connective tissue, made of tough protein fibers, that provides a smooth surface for the movement of bones at joints.

▪A ligament is a band of fibrous connective tissue that holds bones together and keeps them in place.

◇ Blood

Blood is a fluid connective tissue. It circulates throughout the body through blood vessels by the pumping action of the heart. Cells in the blood include red blood cells, white blood cells, and platelets.

■.Nervous tissue is made up of the nerve cells (neurons) that together form the nervous system, including the brain and spinal cord.The cell body contains the nucleus and other cell organelles.

◇ Dendrites extend from the cell body and receive nerve impulses from other neurons.

◇ Axon is a long extension of the cell body that transmits nerve impulses to other cells. The axon branches at the end, forming axon terminals. These are the points where the neuron communicates with other cells.