Types of Cells and Tissues - AP Biology

Cell junctions are common in epithelial tissue because they allow for communication and contact between neighboring cells.

During embryological development, epithelial tissue develops from all three germ layers (endoderm, mesoderm, and ectoderm).

The infolding of epithelial tissue forms glands that function in the exocrine and endocrine systems. Glands secrete products that are taken up by the circulatory system for delivery.

Epithelial tissue has a sensory detection function that utilizes cilia to sense signals from the external environment. Once the signal is recognized and transduced, epithelial cells secrete messenger proteins that transmit the signal downstream.

Skeletal muscle tissue is one of three types of muscle tissue. Skeletal muscle, as the name implies, is anchored to bones by tendons and controls skeletal movement and posture.

Type IIa skeletal muscle tissue is a subtype of skeletal muscle tissue that is related to fast twitch muscles. Type IIa tissues are aerobic and have many mitochondria.

Neuron cells are functional units of nervous tissue that transmit electrical signals. Neurons typically are composed of a soma, dendrites, and an axon. The soma is the body of the cell, the dendrites are branched projections that receive signals, and the axon conducts signals away from the cell body.

The connective tissue is found throughout the body in between other tissues and cell types. Connective tissue functions to both connect and separate the different tissue types.

The somatic nervous system is a part of the peripheral nervous system and controls voluntary body movements. The central nervous system involves only the brain and spinal cord. The autonomic nervous system is not under voluntary control.

Connective tissue has three main components: fibers, ground substance, and cells (fibroblasts, adipocytes, macrophages, mast cells, and leukocytes). Typically, connective tissue contains a relatively low proportion of cells, and a very high proportion of ground substance and fibrous proteins, such as collagen. Blood and lymph is sometimes considered a component of connective tissue as well.

Epithelial cells can be categorized by morphology, or shape. Epithelial cells exist in the following morphologies: squamous, columnar, or cuboidal.

Epithelial cells have three distinct morphologies: squamous, cuboidal, and columnar. Squamous cells are wider than they are tall. In other words, they are flat.

Squamous cells are flat and wide. Both stratified and simple squamous epithelia will form smooth and flat surfaces that are specialized for the simple diffusion across the layer. Squamous cells are found in lung epithelia, the lining of blood vessels, and in the lining of body cavities.

Cuboidal epithelial cells are one category of epithelial cell types. These cells have equal height and width; therefore, they are cube-shaped. They possess round nuclei and are typically involved in secretion and absorption. Cuboidal epithelial cells are located in the exocrine system.

Epithelial cuboidal cells are involved in secretion and absorption in the exocrine system in the lining of glands.

Epithelial columnar cells represent one type of epithelial cell morphology. Columnar cells are taller than they are wide, have elongated nuclei, and are pillar-like. Epithelial columnar cells play a role in the digestive system and are important in sensory reception.

Epithelial columnar cells secrete digestive enzymes and absorb food in the digestive system and they also play a role in sensory reception. Epithelial columnar cells can be found in the tongue, ear, and the lining of the intestine.

Cartilage, rather than bone, forms the fetal skeleton and is softer and more flexible than bone. Unlike cartilage, bone has both vascular and nervous networks running through it.

Osteoblasts contribute to the ossification process by working to build bone. They cannot do so as individual cells, but rather need to be arranged into osteons in the bone to function. Osteoblasts are regulated by a number of factors depending on the body's need for bone creation or resorption, including being inhibited by PTH.