Human Physiology

Lesson 02 : Cell Functions, Cell Types

Specialized Cell of the Human Body

Although there are specialized cells - both in structure and function - within the body, all cells have similarities in their structural organization and metabolic needs. Different types of specialized cells in the human body are the following.

Nerve Cells: Also calledNeurons these cells are present in the nervous system and these functions to process and transmit information. They are the core components of brain, spinal cord and peripheral nerves connected through chemical and electrical synapses to relay signals throughout the body.

Epithelial cells: Functions of epithelial cells include secretion, absorption, protection, transcellular transport, sensation detection, and selective permeability. Epithelium lines both the outside (skin) and the inside cavities and lumen of hollow organs.

Exocrine cells: These cells secrete products through ducts; such as mucus, sweat, or digestive enzymes. The products of these cells go directly to the target organ through the ducts. For example, the bile from the gall bladder is carried directly into the duodenum via the bile duct.

Endocrine cells: These cells are similar to exocrine cells, but secrete their products directly into the bloodstream without a duct. Endocrine cells are found throughout the body but are concentrated in hormone-secreting glands such as the pituitary. The products of the endocrine cells go throughout the body in the blood stream but act on specific organs by receptors on/in the cells of the target organs. For example, the hormone estrogen acts specifically on the uterus and breasts of females because there are estrogen receptors in the cells of these target organs.

Blood Cells: The most common types of blood cells are: Red blood cells (erythrocytes): The main function of red blood cells is to collect oxygen in the lungs and deliver it through the blood to the body tissues. Gas exchange is carried out by simple diffusion

White blood cells (leukocytes): They are produced in the bone marrow and help the body to fight infectious disease and foreign objects in the immune system White cells are found in the circulatory system, lymphatic system, spleen, and other body tissues.