Chapter 3 - Tissues Flashcards
Epithelium
a sheet of cells that covers a body surface or lines a body cavity
Epithelial Functions
Protection of the underlying tissues
Secretion (release of molecules from cells)
Absorption (bringing small molecules into cells)
Diffusion (movement of molecules down their concentration gradient)
Filtration (passage of small molecules through a sieve-like membrane)
Sensory reception
6 Unique Characteristics of Epithelial Tissue
Cellularity. Epithelia are composed almost entirely of cells. These cells are separated by a minimal amount of extracellular material, mainly projections of their integral membrane proteins into the narrow spaces between the cells.
Specialized cell junctions. Adjacent epithelial cells are directly joined at many points by special cell junctions.
Polarity. All epithelia have a free apical surface and an attached basal surface. The structure and function of the apical and basal surfaces differ, a characteristic called polarity. The apical surface abuts the open space of a cavity, tubule, gland, or hollow organ. The basal surface lies on a thin supporting sheet, the basal lamina, which is part of the basement membrane
Support by connective tissue. All epithelial sheets in the body are supported by an underlying layer of connective tissue.
Avascular but innervated. Whereas most tissues in the body are vascular (contain blood vessels), epithelium is avascular, meaning it lacks blood vessels. Epithelial cells receive their nutrients from capillaries in the underlying connective tissue. Although blood vessels do not penetrate epithelial sheets, nerve endings do; that is, epithelium is innervated.
Regeneration. Epithelial tissue has a high regenerative capacity. Some epithelia are exposed to friction, and their surface cells rub off. Others are destroyed by hostile substances in the external environment such as bacteria, acids, and smoke. As long as epithelial cells receive adequate nutrition, they can replace lost cells quickly by mitosis, cell division
Classification of Epithelia
Epithelia can be simple (Only have one layer of cells) or Stratified (be made of many layers)
Shapes of cells can be squamous (flat cells with flat, disc-shaped nuclei.), cuboidal (spherical, with centrally located nuclei), or columnar (wide, like columns)
Function of Epithelial Tissue Related to Tissue Type
Simple Squamous Epithelia Description
Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm
the simplest of the epithelia
Simple Squamous Epithelia Function
Allows materials to pass by diffusion and filtration in sites where protection is not important
secretes lubricating substances in serosae
Simple Squamous Epithelia Location
Kidney glomeruli, air sacs of lungs, lining of heart, blood vessels, and lymphatic vessels, lining of ventral body cavity (serosae)
Simple Cuboidal Epithelia Description
Single layer of cubelike cells with large, spherical central nuclei
Simple Cuboidal Epithelia Function
Secretion and absorption
Simple Cuboidal Epithelia Location
Kidney tubules; ducts and secretory portions of small glands; ovary surface
Simple Columnar Epithelia Description
Single layer of tall cells with round to oval nuclei some cells bear cilia layer may contain mucus-secreting unicellular glands (goblet cells)
Simple Columnar Epithelia Function
Absorption
secretion of mucus, enzymes, and other substances
ciliated type propels mucus (or reproductive cells) by ciliary action
simple Columnar Tissue Locaions
Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus
Psuedofied Columnar Epithelia Description
Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting goblet cells and bear cilia.
Psuedofied Columnar Epithelia Function
Secretes substances, particularly mucus; propulsion of mucus by ciliary action.
Psuedofied Columnar Epithelia Locations
Rare in the body
Nonciliated type in male’s sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract.
Stratified Squamous Epithelia Description
stratified squamous epithelium consists of many cell layers whose surface cells are squamous. In the deeper layers, the cells are cuboidal or columna
Stratified Squamous Epithelia Location
It covers the often-abraded surfaces of our body, forming the epidermis of the skin and the inner lining of the mouth, esophagus, and vagina. To learn the location of stratified squamous epithelium, simply remember that this epithelium forms the outermost layer of the skin and extends a certain distance into every body opening that is directly continuous with the skin.
The epidermis of the skin is keratinized, meaning that its surface cells contain an especially tough protective protein called keratin. The other stratified squamous epithelia of the body lack keratin and are nonkeratinized.
Stratified Squamous Epithelia Function
Of all the epithelial types, this is the thickest and best adapted for protection.
Stratified Cuboidal Epithelia Description
Generally has 2 layers of cubelike cells
Stratified Cuboidal Epithelia Function
Secretion and Protection
Stratified cuboidal Epithelia Location
Located in the large ducts of some glands, for example, sweat glands, mammary glands, and salivary glands.
Stratified Columnar Epithelia Description
Several cell layers; basal cells usually cuboidal; superficial cells elongated and columnar
Stratified Columnar Epithelia Description
Secretion and Protection
Stratified Columnar Epithelia Location
located in the large ducts of some glands, for example, sweat glands, mammary glands, and salivary glands. Also found in small amounts in the male urethra
Glands
A structure who’s cells are specialized for secretion. There are both endocrine lands and exocrine
Secretion
a process by which substances are produced and discharged from a cell, gland, or organ for a particular function in the organism or for excretion.
The protein product is made in the rough endoplasmic reticulum (ER), then packaged into secretory granules by the Golgi apparatus and ultimately released from the cell by exocytosis
Endocrine Glands
Glands within the body that secrete directly into the tissue fluid that surrounds them. More specifically, endocrine glands produce messenger molecules called hormones, which they release into the extracellular space. Endocrine glands are ductless
Exocrine Glands
secrete their products onto body surfaces or into body cavities
multicellular exocrine glands have ducts that carry their product to the epithelial surfaces.
The activity of an exocrine secretion is local. Exocrine glands are a diverse group: They include many types of mucus
Unicellular Exocrine Glands
The only major one-celled exocrine gland in humans is the goblet cell. True to its name, a goblet cell is indeed shaped like a goblet, a drinking glass with a stem.
Goblet cells are scattered within the epithelial lining of the intestines and respiratory tubes, between columnar cells with other functions.
They produce mucin (mu′sin), a glycoprotein (sugar protein) that dissolves in water when secreted. The resulting complex of mucin and water is viscous, slimy mucus. Mucus covers, protects, and lubricates many internal body surfaces.
Multicelular Exocrine glands
Each multicellular exocrine gland has two basic parts: an epithelium-walled duct and a secretory unit consisting of the secretory epithelium. Also, in all but the simplest glands, a supportive connective tissue surrounds the secretory unit, carrying with it blood vessels and nerve fibers
Multicellular glands are classified by the structure of their duct
Tight Junctions
At tight junctions, the adjacent cells are so close that some proteins in their plasma membranes are fused. This fusion forms a seal that closes off the extracellular space; thus tight junctions prevent molecules from passing between the cells of epithelial tissue
Desmosomes
These adhesive spots are scattered along the abutting sides of adjacent cells (Figure 4.6b). Desmosomes have a complex structure: On the cytoplasmic face of each plasma membrane is a circular plaque. The plaques of neighboring cells are joined by linker proteins. These project from both cell membranes and interdigitate, like the teeth of a zipper, in the extracellular space. In addition, intermediate filaments (the cytoskeletal elements that resist tension) insert into each plaque from its inner, cytoplasmic side.
Gap Junctions
a tunnel-like junction that can occur anywhere along the lateral membranes of adjacent cells (Figure 4.6c). Gap junctions function in intercellular communication by allowing small molecules to move directly between neighboring cells. At such junctions, the adjacent plasma membranes are very close, and the cells are connected by hollow cylinders of protein (connexons). Ions, simple sugars, and other small molecules pass through these cylinders from one cell to the next.
Microvilli
Fingerlike extensions of the plasma membrane of apical epithelial cells (Figure 4.7). Each microvillus contains a core of actin filaments that extend into the network of actin microfilaments of the cytoskeleton, called the terminal web. These actin filaments function to stiffen the microvillus.
most abundant on epithelia that absorb nutrients (in the small intestine) (Figure 4.3c) or transport ions (in the kidney). In such epithelia, microvilli maximize the surface area across which small molecules enter or leave cells. Microvilli are also abundant on epithelia that secrete mucus, where they help anchor the mucous sheets to the epithelial surface.
Nervous Tissue Description
Contains neurons which branch off often. When looking at them, look for a dense neuron process and it’s branches
Skeletal Muscle Tissue
Cardiac Muscle Tissue
Smooth Muscle Tissue
lookForCigarShapes.
Bone Tissue
Blood Tissue
Hyaline Cartilage
Elastic Cartilage
