Animal cells and Tissues
The building unit for animals is also cells. A group of same cells form a tissue, several types of tissues form an organ which performs certain function, and several organs form an organ system to perform a more complete function. 11 major organ systems together form a vertebrate animal. Animals have four major tissue types:
1) Epithelial Tissue --closely packed in either single or multiple layers, and cover both internal and external surfaces of the animal body. The function of epithelial layer is movement materials in, out, or around the body; protection of the internal environment against the external environment; secretion of a product.
2) Connective Tissue --tissue with an extensive extra cellular matrix and often serves to support, bind together, and protect organs. The function of connective tissues is binding, supporting, protecting, forming blood storing fats, and filling space. Blood and bones are specialized connective tissues.
3) Muscle Tissue--formed by muscle cells for movement of and/or within the animal. Cardiac muscle is striated muscle found only in the heart. The cells are usually connected to each other by intercalated disks. It powers the heartbeat.
4) Nervous Tissue --bundles of neuronal processes enclosed in connective tissue that carry signals to and from muscles. Nervous tissue is made up of two types of cells: neurons and glial cells. A neuron is made up of three parts: A cell body which contains the nucleus, mitochondria and other organelles; An anon which is a long fiber that carries signals away from the cell body and many dendrites which receive information from another cell and transmit the message to the cell body.
Animal Organ System
Organs are grouped together according to their functions.
Muscle system is composed of all skeleton-attached muscles. The function of muscle system is movement and locomotion, powering circulatory, digestive, and respiratory systems, and plays a role in regulating temperature.
Digestive system is composed of mouth, esophagus, stomach, small intestine, liver, pancreas, gallbladder, colon (large intestine), rectum, and anus. The function of digestive system is ingesting food and breaking it down into smaller chemical units; absorbing the nutrients; and eliminating solid wastes into the environment.
Respiratory system contains nose, pharynx, larynx, trachea, bronchi, and lung. The major function of respiratory system is exchanging gas between body and environment, which includes inhale oxygen and remove carbon dioxide.
Cardiovascular System is composed of three parts: blood vessels, blood and heart. The function of cardiovascular system is to transport oxygen, carbon dioxide, nutrients, and waste products between cells and the respiratory system and carries chemical signals from the endocrine system.
Lymphatic system is also called immune system. It is composed of central lymphoid tissue and peripheral lymphoid tissue. Function of lymphatic system is defense against invading microorganisms and viruses, and defense against the growth of cancer cells.
Excretory system contains liver, skin and urinary system. The function of excretory system is to remove organic waste and maintain fluid levels.
Endocrine system is composed of all glands including pineal gland, hypothalamus, pituitary gland, thyroid gland, thymus, parathyroid glands, adrenal glands, reproductive gland and pancreas. Function of endocrine system is to secret hormones to control growth and homeostasis, it also coordinate long-range response to external stimuli.
Reproductive systems are different in male and females. The function is secretion of hormones and reproduction.
Nervous system is divided into central nervous system and peripheral nervous system. The central nervous system includes brain and spinal cord. The peripheral nervous system contains all neurons and nerves that are not in the central nervous system. The function of nervous system is to Coordinates the activity of the muscles, to monitor the organs constructs and to Processes input from the senses, and initiates actions.
Skeletal system contains all bones in human body and the majority of the bones are internally linked. The function of the skeletal system is to support for the body, producing blood and immune cells, to support muscle movement and to store minerals.
Skin system is made of skin, hair, nail and skin glands and their products. The skin is divided into two layers, epidermis which includes Keratinocytes, basal cells and melanocytes; and Dermis which contains elastic and collagen fibers, capillary networks, and nerve endings. The function of skin system is to for protection, exchange and secretion.
Homeostasis
Homeostasis is defined as living organisms regulating its internal environment to maintain a stable, constant condition, by means of multiple dynamic equilibrium adjustments, controlled by interrelated regulation mechanisms. The mechanism of homeostasis is through a negative feedback response. Normally a threshold is set for triggering certain response. The sensor senses the change and transmits the change via a signal transduction pathway, reaching effectors to bring back the balance. Regulation on blood glucose level is an example.
