Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells.
In biology, homeostasis is the state of steady internal physical and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits. Other variables include the pH of extracellular fluid, the concentrations of sodium, potassium, and calcium ions, as well as the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity. Each of these variables is controlled by one or more regulators or homeostatic mechanisms, which together maintain life.
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Blood vessels are the tubular structures of a circulatory system that transport blood throughout a vertebrate's body. Blood vessels transport blood cells, nutrients, and oxygen to most of the tissues of a body. They also take waste and carbon dioxide away from the tissues. Some tissues such as cartilage, epithelium, and the lens and cornea of the eye are not supplied with blood vessels and are termed avascular.
The human body is the entire structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organs and then organ systems.
The circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels. The circulatory system has two divisions, a systemic circulation or circuit, and a pulmonary circulation or circuit. Some sources use the terms cardiovascular system and vascular system interchangeably with circulatory system.
The integumentary system is the set of organs forming the outermost layer of an animal's body. It comprises the skin and its appendages, which act as a physical barrier between the external environment and the internal environment that it serves to protect and maintain the body of the animal. Mainly it is the body's outer skin.
In biology, tissue is an assembly of similar cells and their extracellular matrix from the same embryonic origin that together carry out a specific function. Tissues occupy a biological organizational level between cells and a complete organ. Accordingly, organs are formed by the functional grouping together of multiple tissues.
The excretory system is a passive biological system that removes excess, unnecessary materials from the body fluids of an organism, so as to help maintain internal chemical homeostasis and prevent damage to the body. The dual function of excretory systems is the elimination of the waste products of metabolism and to drain the body of used up and broken down components in a liquid and gaseous state. In humans and other amniotes, most of these substances leave the body as urine and to some degree exhalation, mammals also expel them through sweating.
In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific function. The intestinal wall for example is formed by epithelial tissue and smooth muscle tissue. Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system.
The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates internal organs, smooth muscle and glands. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, its force of contraction, digestion, respiratory rate, pupillary response, urination, and sexual arousal.
Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrates, this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell. For example, placental mammals expel urine from the bladder through the urethra, which is part of the excretory system. Unicellular organisms discharge waste products directly through the surface of the cell.
The microcirculation is the circulation of the blood in the smallest blood vessels, the microvessels of the microvasculature present within organ tissues. The microvessels include terminal arterioles, metarterioles, capillaries, and venules. Arterioles carry oxygenated blood to the capillaries, and blood flows out of the capillaries through venules into veins.
In cell biology, extracellular fluid (ECF) denotes all body fluid outside the cells of any multicellular organism. Total body water in healthy adults is about 50–60% of total body weight; women and the obese typically have a lower percentage than lean men. Extracellular fluid makes up about one-third of body fluid, the remaining two-thirds is intracellular fluid within cells. The main component of the extracellular fluid is the interstitial fluid that surrounds cells
Loose connective tissue, also known as areolar tissue, is a cellular connective tissue with thin and relatively sparse collagen fibers. They have a semi-fluid matrix with lesser proportions of fibers. Its ground substance occupies more volume than the fibers do. It has a viscous to gel-like consistency and plays an important role in the diffusion of oxygen and nutrients from the capillaries that course through this connective tissue as well as in the diffusion of carbon dioxide and metabolic wastes back to the vessels. Moreover, loose connective tissue is primarily located beneath the epithelia that cover the body surfaces and line the internal surfaces of the body. It is also associated with the epithelium of glands and surrounds the smallest blood vessels. This tissue is thus the initial site where pathogenic agents, such as bacteria that have breached an epithelial surface, are challenged and destroyed by cells of the immune system.
Equine anatomy encompasses the gross and microscopic anatomy of horses, ponies and other equids, including donkeys, mules and zebras. While all anatomical features of equids are described in the same terms as for other animals by the International Committee on Veterinary Gross Anatomical Nomenclature in the book Nomina Anatomica Veterinaria, there are many horse-specific colloquial terms used by equestrians.
Shark anatomy differs from that of bony fish in a variety of ways. Variation observed within shark anatomy is a potential result of speciation and habitat variation.
Insect physiology includes the physiology and biochemistry of insect organ systems.
Fish physiology is the scientific study of how the component parts of fish function together in the living fish. It can be contrasted with fish anatomy, which is the study of the form or morphology of fishes. In practice, fish anatomy and physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in the living fish.
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion. Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The process of digestion has three stages: the cephalic phase, the gastric phase, and the intestinal phase.
