ORGANS AND ORGAN SYSTEM
Organ
The group of different tissues performing same function is called organs. Different tissues are organized into the organs except simplest animals (sponges and cnidarians). Some organs have their tissue layers. For example, the stomach has four major layers.
- The lumen is lined by a thick epithelium. This epithelium secretes mucus and digestive juices.
- Outside this layer is a zone of connective tissue
- It is followed by a thick layer of smooth muscle.
- The entire stomach is encapsulated by another layer of connective tissue A laminated organization is also present in the dermis. It is the outer skin of the body.Man of the organs of vertebrates are suspended by mesenteries. Mesenteries are heets of connective tissue present in the body cavities. Mammals have an upp r thoracic cavity separated from a lower abdominal cavity by a sheet of must le called the diaphragm.
0 an system
The group of different organs performing same functions is called organ sys m. Organ system is a level of organization higher than organs. The organs car out major functions of vertebrates and members of most invertebrate phyla. Org n system consists of several organs. Examples are the digestive, arc latory. respiratory, and excretory system. Each system has specific func ions. But the efforts of all systems must be coordinated for the survival of ani als. For instance, nutrients are absorbed from the digestive tract. They are distr buted throughout the body by the circulatory system. But the heart itself dep nds on nutrients absorbed by the digestive tract. The respiratory system abs rbs oxygen from the air. This oxygen is transported by blood.
DEFINITIONS AND KEY POINTS
I DEFINITIONS ITERMS Homoeostasis The maintenance of a constant internal environment despite fluctuations in the external environment is called homoeostasis.
Simple diffusion The movement of molecules from the area of higher concentration to the area of lower concentration is called simple diffusion. Fac diffusion litated ., ,
The movement of molecules through the protein molecules from higher to lower concentratiOn is called
facilitated diffusion.OsmoSis The diffusion of water across a selectively permeable ----------------------------
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membrane from an area of higher concentration to an area of lower concentration is called osmosis.
Tonicity The relative concentration of solutes in the water inside and outside the cell is called tonicity Filtiation Filtration is a process that forces small molecules across selectively permeable membranes with the help of
hydrostatic pressure.Act ye transport The movement of molecules form the area of lower concentration to the area higher concentration by the
expenditure of energy is called active-transport.Enc ocytosis The movement of substance inside the cell by infolding of the membrane and formation of vacuole is called endosytosis. The nonspecific uptake of all droplets of extracellular fluid is called pinocytosis.
Pinocytosis Phagocytosis The uptake of solid particles by invagination is called Phagolysosome Lysosome combines with the food vacuole to form a phagolysosome. Exocytosis The removal of cell secretions from the cells by out folding is called exocytosis. Lysosome Lysosome is a membrane-enclosed bag of hydrolytic enzymes that the cell uses to digest macromolecules..
Tissues The sheets of tightly packed cells are called epithelial Connective tissues The tissue, with loose arrangement of cells and the cells are scattered in an extracellular matrix are called
connective tissue.
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