The body is constituted of different types of cells which unite together to form contrary tissues. Tissues are a group of similar cells and their intercellular substance specialized to perform a specific function; primary tissue types of the body are epithelial, connective, muscle, and nervous tissue. Epithelial is pertaining to a primary tissue that covers the body surface, lines its internal cavities, and forms glands. The connective tissue is also a primary tissue; form and function vary extensively. Functions include support, storage and protection (Marieb, E. N., 1998, P.109)
Epithelium occurs in the body as (1) covering and lining epithelium and (2) glandular epithelium. Covering and lining epithelium forms the outer layer of the skin, dips into and lines the open cavities of the cardiovascular, digestive, and respiratory systems, and shelters the walls and organs of the closed ventral body cavity . Glandular epithelium customs the glands of the body .
Epithelium is broadly disseminated throughout the body; its functions are many and varied to perform specific roles. Its functions include protection, absorption, secretion, filtration, excretion and sensory reception. Protection is covering or lining the body surface both internal and external. Absorption is the process by which products of digestion pass through the alimentary tube mucosa into the blood or lymph (protein-containing fluid transported by lymphatic vessels). Secretion is 1. The passage of material formed by a cell to its exterior; 2. Cell product that is transported to the exterior of a cell. Filtration is the passage of a solvent and dissolved substances through a membrane or filter. Excretion involves elimination of waste products from the body. Sensory reception which is dendritic end organs, or parts of other cell types, specialized to respond to a stimulus (Marieb, E.N.1998, p111-116).
The classification of epithelia differs; each epithelium is given two names 1. The number of cell layers present and 2. Describes the shape of the cell.
Simple epithelium is a single layer of cells which functions include diffusion and filtration. The location of this cell is covering visceral organs, linings of lumina and body cavities.
Simple squamous epithelium (refer to fig1, p5) is a single layer of flattened, tightly bound cells which are located in capillary walls; alveoli of lungs; covering visceral organs, lining of body cavities. The function of this tissue is diffusion and filtration.
Simple cuboidal epithelium (refer to fig2, p5) is a single layer of cube shaped cells located on the surface of ovaries; linings of renal tubules, salivary ducts, and pancreatic ducts. Its functions are excretion, secretion and absorption.
Simple columnar epithelium is a single layer of nonciliated, tall, columnar shaped cell located on the lining of GI tract (refer to fig3, p6). This tissue protects secrets and absorbs (Marieb, E.N.1998, p112).
Simple ciliated columnar epithelium is a single layer of ciliated, columnar shaped cells, situated lining the lumen of the uterine (refer to fig4, p7), functioning the transportative role through ciliary motion (Marieb, E.N, 1998,p112).
Pseudostratified ciliated columnar epithelium is a single layer of ciliated, irregular cells that protect, secret. This particular tissue is located on the lining of respiratory passageways (Kent & Van De & Fox, 1995,p116) (refer to fig5 p8). Coughing, sneezing, or simply clearing the throat are protective reflex mechanisms for clearing the respiratory passages of obstructions or inhaled particles that have been trapped in the mucus along the ciliated lining.
Stratified epithelia have two or more layers of cells that protect, strengthen or distension. This tissue is located on the epidermal layer of the skin; linings of body openings, ducts, and urinary bladder (Marieb, E.N, 1998,p114).
Stratified squamous epithelium (keratinized) has numerous layers containing keratin, outer layers flattened and dead. It is found on the epidermis of skin, the function is to protect (Marieb, E.N, 1998,p114).
Stratified squamous epithelium (nonkeratinized) (Refer to fig6, p9) also has numerous layers lacking keratin; outer layers moistened and alive. This tissue function is protection and pliability, and is located on linings of oral anus nasal cavities, vagina, anus and anal canal (Bevan.Dr 1995 p12). This tissue is the first line of defense against entry of living organisms into the body eg: helps prevent diseases.
Stratified cuboidal epithelium (refer to fig7, p10) usually has two layers of cube-shaped cells that are located on large ducts of sweat glands, salivary glands and pancreas. The function of this tissue is to strengthen luminal walls (Kent & Van De & Fox, 1995,p114).
Transitional epithelium (refer to fig8, p11) has numerous layers of rounded, nonkeratinized cells situated on the laminal walls of ureters and urinary bladder and its function is distension (Kent & Van De & Fox, 1995, p114)
CONNECTIVE TISSUE: (Refer to fig9, p12)
Connective tissue is found everywhere in the body. Connective tissue is the most abundant and widely distributed tissue of the body (Mareib, E.N, 1998, P119). Its functions included support, protection, binding, insulation, and transportation of blood (refer to fig pg4).
Characteristic of connective tissues is they emanate from embryonic mesenhyme and exhibit matrix. Depending on what type, a connective tissue may be well vascularized (most), poorly vascularized (dense connective tissue), or avascular (cartilage) (Marieb, E. N., 1998, P140.).
The structural elements of all connective tissues are extacellular matrix (nonliving material that separates the living cells in connective tissue consisting of ground substance and fibers) and cells (Marieb, E.N, 1998 P140).
Another structural element is that each connective type has a primary cell type that can exist as a mitotic, matrix-secreting cell (blast; create the matrix) or as a mature cell (cyte; maintain it) responsible for maintaining the matrix. The chief cell type of connective tissue proper is the fibroblast; (young, actively mitotic cell that forms the fibers of connective tissue) that of cartilage is the chondroblast; that of bone is mocytoblast or hematopoietic stem cell . (Marieb, E.N, 1998, P140&1148).
There are many types of connective tissues (refer to fig pg ) all consisting of living cells surrounded by a matrix, but the major difference reflected is that of cell type, fiber type, and the protection of the matrix contributed by fibers (Dr Bevan, J, 1995 Pg12).
The types of connective tissue include embryonic, connective tissue proper which consists of loose and dense varieties. The loose connective tissues are (areolar, adipose, reticular). Dense connective tissue proper includes (dense regular, dense irregular). Cartilage exists as (hypaline, elastic cartilage and fibrocartilage), bone (osseous tissue) and blood (plasma) (Mabieb, E.N, 1998 P140). As mentioned previously the above are all connective tissues, but they function different parts of the human body.
Now to discuss the types of connective tissues, there features and functions in depth.
An embryonic connective tissue is a gel like ground subtance containg fibers, which usually arises during the early weeks of embryonic development and eventually differentiates into all other connective tissue (Marieb, E.N.1998, p122). This tissue is located in the embryo and functions by giving rise to all other connective tissue types.
Connective tissue proper
Loose connective (areolar) tissue (refer to fig10, p13) has predominantly fiber blast cells with lesser amounts of collagen and elastin proteins. The functions include binding organs and holding tissue fluids, which is located in nerves and vessels, between muscles and beneath the skin. Even though the irregular arrangement of this tissue it provides flexibility, yet strength, in any direction (Kent &Van De & Fox. 1995 p123), this is seen when a body part is rubbed and the tissue allows the skin to move.
Dense regular connective tissue are densely packed collagenous fibers (tendon) (refer to fig11 P14.) lying parallel to the direction of force placed on this tissue during body movement (Marieb, E.N, 1998,p125). The function of this tissue is it provides strong, flexible support, which is located in the tendons and ligaments.
Dense irregular connective tissue is densely packed collagenous fibers arranged in a tight interwoven pattern providing tensile strength in any direction (Marieb, E.N, 1998,p125). The function of this tissue is located in the dermis of skin, fibrous capsules of organs and joints. (Refer to fig12, p15)
Reticular connective tissue is fibers that form supportive network; its function is to support many free blood cells in the lymph nodes, the spleen and bone marrow (Marieb, E.N, 1998,p125) .
Adipose connective tissue protects organs, store fat, insulates against heat loss, and is located in the hyodermis of skin, surface of heart, omentum, around kidneys, back of eye ball and surrounding joints (Marieb, E.N, 1998,p126).
Hyaline cartilage is the most abundant cartilage within the body. It covers the articular surfaces of bones, supports the tubular trachea and forms the flexible bridge called costal cartilage, between the ventral end of each of the first ten ribs and the sternum (Marieb, E.N, 1998,p127). It supports and reinforces, has resilient cushioning properties and resists compressive stress.
Fibrocartilage is a durable tissue, adapted to withstand tension and compression. It is found at the symphysis pubis, where the two pelvic bones articulate, and between the vertebrae as intervertebral discs. It also forms the cartilaginous wedges within the knee joint, call menisci (Kent &Van De & Fox. 1995 p126). For example by the end of the day, the intervertebral discs of the vertebral column are somewhat compacted. So a person is actually slightly shorter in the evening than in the morning following a recuperative rest. With aging comes a gradual and irreversible compression of the fibrocartilaginous discs.
Elastic cartilage is similar to hyaline, but more elastic fibers in matrix. It is located in the external ear that allows the function of maintaining the shape of a structure while allowing flexibility (Marieb, E.N, 1998,p129).
Bone (osseous tissue) is a hard, calcified matrix containing many collagen fibers and is located in the bones. The functioning of this tissue is bone support and protection, providing levers for the muscles to act on, stores calcium and other minerals and fat (Marieb, E.N, 1998,p129).
Blood is red and white blood cells in a fluid matrix. Its located, contained within blood vessels. The function of blood is the transportation of respiratory gases, nutrients, wastes, and other substances (Marieb, E.N, 1998,p130).
DISEASES CAUSED DUE TO DISTURBANCES IN THE FUCTIONING OF
CELLS AND TISSUE
The skin is composed of two major layers. The outer layer, the epidermis, (Superficial layer of the skin; composed of keratinized stratified squamous epithelium) is mainly responsible for protection. The inner layer, the dermis, forms the structural foundation and gives the skin its mechanical strength and elasticity. These two layers lie on top of a fat layer, which provided a soft, cushioning coutour to the body.
An injured or diseased epidermis can cause greater than normal water evaporation, producing cracking and dryness. This enables chemicals and/or infection to penetrate the skin, leading to deeper damage skin cancer .
The skin is constantly exposed to environmental hazards, especially ultraviolet light. Ultraviolet A light is likely to cause damage within the dermis, leading to wrinkles and premature aging, while B light is more likely to cause skin cancer.
In order for the human body to function both epithelium and connective tissues are needed. These tissues play/ perform major function within our body, in order for us to live and protects humans from harmful diseases within our environment.
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