Provide physical protection Control permeability Provide sensation Produce specialized secretions There are various specialized types of epithelia. They can be sorted by cell shape and the number of cells between the basement membrane and the exposed surface of the epithelium. The three basic shapes of epithelial are squamous, cuboidal, and columnar. If the basement membrane is only covered by one layer of cells it is called a simple epithelium. If the basement membrane is cover by several layers of cells it is called stratified epithelium.
There are many structures of epithelial tissue, however I will only briefly cover four of them, these are squamous ,cuboidal, columnar and compound cells. http://kidsresearchexpress-5.blogspot.co.uk/2008/08/tissue.html Squamous Epithelial Cells Squamous cells are flat and they fit closely together, they don’t offer much protection as they are quite delicate and thin. Due to their thin construction, this allows small molecules to easily diffuse through the cell. This type of epithelial tissue can be found in places where rapid diffusion takes place such as the kidneys as they diffuse up to 180 litres of blood every day. http://www.bio.davidson.edu/people/kabernd/berndcv/lab/epithelialinfoweb/simple%20squamous%20epithelium.html Cubodial Epithelial Cells Cubodial cells are obviously shaped like a cube, hence the name.
Nervous tissues are found is all organs in the body some have more than others thought, Maximum in the nervous system, least in fatty deposits. Some examples are brain which is a main nervous tissue but also an organ also the heart that is one of our most important organ but also a nervous tissue. Here’s a labelled picture of a nervous tissue; http://biologyonline.us/Online%20A&P/AP%202/Northland/AP2lab/Lab%201%20online/lab1/images/Picture14.jpg Epithetical tissue The function of the epithetical tissue include transportation of materials, protection of underlying tissues, absorption of water and nutrients and secretions of waste products. Epithelial tissue covers the whole surface of the body. It is made up of cells closely packed and ranged in one or more layers.
Introduction All cells have plasma membranes which are selectively permeable meaning only some materials are able to move across it either to enter or exit the cell. The ability of a molecule to cross the plasma membrane depends on its size, hydrophobicity and charge as well as the relative concentration inside and outside of that cell (Biology Department, 2010). When molecules move from high concentration to low concentration it is called diffusion. More specifically when water diffuses across a cell membrane it is called osmosis. If the concentration of water in a cell is lower than the concentration of water in the solute the solution is said to be hypotonic and the cells swell because they will take up water.
The elodea cells are very small and round. They are all connected together to make a sheet of little cells. All is very uniform and precise. The onion had cells that looked like boxes. They didn’t line up very well and they just weren’t as precise as the elodea cell was.
Comb jellies have incomplete digestive tracts and excretion is done either through the mouth or anus. Although they lack a brain, they do have a sub-epidural nerve net. Ctenophores have an epidermis and a
The cell membrane is semi-permeable because it allows some substances to pass through and some substances cannot pass. Small molecules such as water, glucose, and amino acids can pass through the membrane while large molecules such as starch cannot pass through. Active transport is the movement of a particle against its concentration gradient (requires energy). Passive transport is the movement of molecules across the membrane (does not requires energy). Diffusion is the movement of molecules without the use of energy.
Endoderm forms the lining of the gut, respiratory tract, and urinary bladder. It also forms the glands associated with the gut and respiratory tract. Junctions Cells are joined to each other by proteins. The point of connection between two cells is called a junction. Junctions bind cells together.
In mammals this forms a circulatory system of arteries, capillaries and veins. In flowering plants, transport is not circulatory and occurs in microscopic xylem and phloem. Both transport systems use water as the basis for transport since it is a good solvent, has a high specific heat capacity, is not too viscous and is unreactive (inert). Both animals and plants have more than one type of tissue which is specialised to make transport an efficient process. The vessels and tracheids in xylem are made up of dead, lignified cells.
Epithelium is an avascular tissue and has no integral (direct) blood supply. FUNCTIONS OF EPITHELIUM: Owing to the strategic location of epithelium at the border between the internal and external environments, the functions of epithelium are many and varied, but can be conveniently divided into two major categories: protective or metabolic. Protective functions of epithelium include protection against: * mechanical damage * loss of fluids (desiccation) - waterproofing * invasion of foreign bodies ( e.g. skin) Metabolic functions of epithelium include: * Exchange of metabolites, typically described as ion-transport. All the substances entering or leaving the body must pass through epithelium and are under its control.