Description: Single layer of nonciliated columnlike cells with oval nuclei near base of cells. Contains (1) columnar eppithelium cells with microvili at apical surface and (2) gobelt cells. Microvili, fingerlike cytoplasmic projections, increase surface area of plasma membrane, thus increasing cell's rate of absorption. Goblet cells are modified columnar epithelial cells that secrete mucus, a slightly sticky fluid, at thier apical surfaces.Before release, mucus accumulates in upper portion of cell, causing it to bulge and making the whole cell resemble a goblet or wine glass.
Location: Lines gastrointestinal tract (from stomach to anus), ducts of many glands and gallbladder.
Function: Secretion and absorption; large columnar cells contain more organelles and thus are capable of higher level secretion and absorption than are cuboidal cells. Secreted mucus lubricates linings of digestive, respiratory, and reproductive tracts, and most of urinary tract; helps prevent destruction of stomach lining by acidiv gastric juice secreted by stomach.
Description: Two or more layers of cells; cells in an apical layer and several layers deep to it are squamous; cells in deeper layers vary from cuboidal ro columnar. A basal cells divide, daughter cells arising from cell divisions push upward toward apical layer. As they move toward surface and away from blood supply in underlying connective tissue, they become dehydrated and less metabolically active. Tough proteins predominate as cytoplasm is reduced, and cells become tough, hard structures that eventually die. At apical layer, after dead cells lose cell junctions they are sloughed off, but they are replaced continuously as new cells emerge from basal cells.
Keratinized stratified squamous develops tough layers of keratin in apical layer of cells and several layers deep to it. Relative amount of keratin increases in cells as they move away from nutritive blood supply and organelles die.
Nonkeratinized stratified squamous does not contain large amounts of keratin in apical layer and several layers deep and is constantly moistened by mucus from salivary and mucous glands; organelles are not replaced.
Location: Keratinized variety forms superficial layer of skin; nonkeratinized variety lines wet surfaces (lining of mouth, esophagus, part or epiglottis, part of pharynx, and vagina) and covers tounge.
Function: Protection against abrasion, water loss, ultraviolet radiation, and foreign invasion. Both types from first line of defense against microbes.
(Mature Connective Tissue; Loose Connective Tissue)
Description: One of the most widely distributed connective tissues; consists of fibers (collagen, elastic, reticular) arranged randomly and several kinds of cells (fibroblasts, macrophages, plasma cells, adipocytes, mast cells, and a few white blood cells) embedded in semifluid groud substance (hylauronic acid, chondroitin sulfate, dermatan sulfate, and keratin sulfate.
Location: In and around nearly every body structure in subcutaneous layer deep to skin; papillary region of dermis of skin; lamina propria of mucous membranes; around blood vessels, nerves and body organs.
(Mature Connective Tissue, Loose Connective Tissue)
Description: Has cells derived from fibroblasts (called adipocytes) that are specialized for storage of triglycerides (fats) as a large, centrally located droplet. Cell fills up with single, large triglyceride droplet, and cytoplasm and nucleus are pushed to periphery of cell. With weight gain, amount of adipocytes increases and new blood vessels form. Thus, and obese person has many more blood vessels than does a lean person, a situation that can cause high blood pressure, since the heart has to work harder. Most adipose tissue in adults in white adipose tissue. Brown adipose tissue (BAT) is darker due to very rich blood supply and numerous pigmented mitochondria that participate in aerobic cellular respiration. BAT is widespread in the fetus and infant; adults only have small amounts.
Location: Wherever areolar connective tissue is located; subcutaneous layer deep to skin, around heart and kidneys, yellow bone marrow, padding around joints and behind eyeball in socket.
Function: Reduces heat loss through skin; serves as an energy reserve; supports and protects organs. In newborns, BAT generates heat to maintain proper body temperature.
(Mature Connective Tissue, Dense Connective Tissue)
Description: Collagen fibers, usually irregularly arranged with few fibroblasts.
Location: Often occurs in sheets, such as fasciae (tissue beneath skin and around muscles and other organs), reticular (deeper) region of dermis of skin, fibrous pericardium of heart, periosteum of bone, perichondrium of cartilage, joint capsules, membrane capsules around various organs (kidneys, liver, testes, lymph nodes); also in heart valves.
Function: Provides tensile (pulling) strength in many directions.
(Mature Connective Tissues: Cartilage)
Description: Hyaline cartilage contains a resiliant gel as ground substance and appears in the body as a bluish-white, shiny substance. Fine collagen fibers are not visible with ordinary staining techniques; prominent chondrocytes are found in lacunae surrounding by perichondrium.
Location: Most abundant carilage in body; at ends of long bones, anterior ends of ribs, nose, pasrts of larynx, trachea, bronchi, bronchial tubes, embryonic and fetal skeleton.
Function: Provides smooth surfaces for movement at joints, flexibility, and support; weakest type of cartilage.
Description: Fibers usually involuntary, nonstriated. Smooth muscle fiber is a small spindle-shaped cell thickest in middle, tapering at each end, and containing a single, centrally located nucleus. Gap junctions connect many individual fibers in some smooth muscles (in wall of intestines). Can produce powerful contractions, as many muscle fibers contract in unison. Where gap junctions are absent, such as iris of eye, smooth muscle fibers contract individually, like skeletal muscle fibers.
Location: Iris of eyes; walls of hollow internal structures such as blood vessles, airways to lungs, stomach, intestines, gallbladder, urinary bladder, and uterus.
Function: Motion (constriction of blood vessels and airways, propulsion of foods through gastrointestinal tract, contraction of urinary bladder, and gallbladder).