Chapter 4 Flashcards
Tissue
A group of cells that usually have a common origin in an embryo and function together to carry out specialized activities.
What are the four basic types of tissues?
Epithelial tissue, connective tissue, muscular tissue, and nervous tissue.
Epithelial tissue
Covers body surfaces and lines hollow organs, body cavities, and ducts; it also forms glands. This tissue allows the body to interact with both its internal and external environments.
Connective tissue
Protects and supports the body and its organs. Various types of connective tissues bind organs together, store energy reserves as fat, and help provide the body with immunity to disease-causing organisms.
Muscular tissue
Is composed of cells specialized for contraction and generation of force. In the process, muscular tissue generates heat that warms the body.
Nervous tissue
Detects changes in a variety of conditions inside and outside the body and responds by generating electrical signals called nerve action potentials (nerve impulses) that activate muscular contractions and glandular secretions.
Cell junctions
Are contact points between the plasma membranes of tissue cells.
What are the five basic types of cell junctions?
Tight junctions, adherens junctions, desmosome, hemidesmosomes, and gap junction.
Tight junctions
Consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells.
Adherens junctions
A dense layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to microfilaments of the cytoskeleton. Adherens junctions help epithelial surfaces resist separation during various contractile activities, as when food moves through the intestines.
Cadherins
Transmembrane glycoproteins that join cells. Each cadherin inserts into the plaque from the opposite side of the plasma membrane, partially crosses the intercellular space (the space between the cells) and connects to cadherins of an adjacent cell.
Adhesion belts
Adherens junctions that encircle a cell (similar to the way a belt encircles your waist).
Desmosome
Contain plaque and have transmembrane glycoproteins (cadherins) that extend into the intercellular space between adjacent cell membranes and attach cells to one another. However, unlike adherens junctions, the plaque of desmosomes does not attach to microfilaments. Instead, a desmosome plaque attaches to elements of the cytoskeleton known as intermediate filaments, which consist of the protein keratin.
Hemidesmosomes
Resemble desmosomes, but they do not link adjacent cells. The transmembrane glycoproteins in hemidesmosomes are integrins rather than cadherins. On the inside of the plasma membrane, integrins attach to intermediate filaments made of the protein keratin. On the outside of the plasma membrane, the integrins attach to the protein laminin, which is present in the basement membrane. Thus, hemidesmosomes anchor cells not to each other but to the basement membrane.
Gap junctions
Contain connexins and connexons. Gap junctions allow the cells in a tissue to communicate with one another.
Connexins
Membrane proteins that form connexons.
Connexons
Tiny fluid-filled tunnels that connect neighbouring cells and allow ions and small molecules to diffuse from the cytosol of one cell to another.
What are the two differences between epithelial and connective tissue?
- The number of cells in relation to the extracellular matrix (the substance between cells). In an epithelial tissue many cells are tightly packed together with little or no extracellular matrix, whereas in a connective tissue a large amount of extracellular material separates cells that are usually widely scattered.
- An epithelial tissue has no blood vessels, whereas most connective tissues have significant networks of blood vessels.
______ almost always forms surface layers and is not covered by another tissue. An exception is ______.
Epithelial tissue, the epithelial lining of blood vessels where blood constantly passes over the epithelium.
Epithelial tissue
Cells arranged in continuous sheets, in either single or multiple layers. The various surfaces of covering and lining epithelial cells often differ in structure and have specialized functions.
What is the functional role of epithelial tissue?
Functionally, epithelial tissue protects, secretes (mucus, hormones, and enzymes), absorbs (nutrients in the gastrointestinal tract), and excretes (various substances in the urinary tract).
Exchange of substances between an epithelial tissue and connective tissue occurs through ______.
Diffusion
A ______ allows epithelial tissue to constantly renew and repair itself.
High rate of cell division.
Basement membrane
is a thin extracellular layer found between an epithelial tissue and a connective tissue; attaches and anchors the epithelium to its underlying connective tissue; consists of two layers, the basal lamina and reticular lamina.
Basal lamina
One of the layers of basement membrane; is closer to, and secreted by, the epithelial cells.
Reticular lamina
One of the layers of basement membrane; is closer to the underlying connective tissue.
What are the two types of epithelial tissue?
Surface epithelium and glandular epithelium
Surface epithelium
Forms the outer covering of the skin and some internal organs. It also forms the inner lining of blood vessels, ducts, body cavities, and the interior of the respiratory, digestive, urinary, and reproductive systems.
Glandular epithelium
Makes up the secreting portion of glands such as the thyroid gland, adrenal glands, sweat glands, and digestive glands.
What are the two characteristics that types of surface epithelium are classified according to?
- Arrangement of layers
- Cell shapes
Simple epithelium
A single layer of cells that functions in diffusion, osmosis, filtration, secretion, or absorption.
Pseudostratified epithelium
Appears to have multiple layers of cells because the cell nuclei lie at different levels and not all cells reach the apical surface; it is actually a simple epithelium because all its cells rest on the basement membrane.
Stratified epithelium
Consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear.
Squamous cells
Are thin, which allows for the rapid passage of substances through them.
Cuboidal cells
Are as tall as they are wide and are shaped like cubes or hexagons. They may have microvilli at their apical surface and function in either secretion or absorption.
Columnar cells
Are much taller than they are wide, like columns, and protect underlying tissues. Their apical surfaces may have cilia or microvilli, and they often are specialized for secretion and absorption.
Transitional cells
Change shape, from squamous to cuboidal and back, as organs such as the urinary bladder stretch (distend) to a larger size and then collapse to a smaller size.
Glandular epithelium
Main function of glandular epithelium is secretion.
Gland
Consists of epithelium that secretes substances into ducts (tubes), onto a surface, or eventually into the blood in the absence of ducts. All glands of the body are classified as either endocrine or exocrine.
Endocrine glands
AKA hormones; endocrine secretions have far-reaching effects because they are distributed throughout the body by the bloodstream.
Exocrine gland
Exocrine secretions have limited effects as some of them would be harmful if they entered the bloodstream; are classified as either unicellular or multicellular.
Unicellular glands
Are single-celled glands (Eg. Goblet cells are important unicellular exocrine glands that secrete mucus directly onto the apical surface of a lining epithelium).
Multicellular glands
Most endocrine glands are multicellular glands; composed of many cells (Eg. sudoriferous (sweat), sebaceous (oil), and salivary glands).
How are multicellular glands categorized?
They are categorized according to two criteria: 1.) whether their ducts are branched or unbranched and 2.) the shape of the secretory portions of the gland.
Simple tubular
Tubular secretory part is straight and attached to a single unbranched duct
Simple branched tubular
Tubular secretory part is branched and attaches to a single unbranched duct.
Simple acinar
Secretory portion is rounded, attaches to single unbranched duct.
Simple branched acinar
Rounded secretory portion is branched and attaches to unbranched duct.
Compound tubular
Secretory portion is tubular and attaches to a branched duct.
Compound acinar
Secretory portion is rounded and attaches to a branched duct.
Compound tubuloacinar
Secretory portion is both tubular and rounded and attaches to a branched duct.
Describe the functional classification of multicellular exocrine glands
The functional classification of exocrine glands is based on whether a secretion is a product of a cell or consists of an entire or partial glandular cell. There are three types: merocrine glands, apocrine glands, and holocrine glands.
Merocrine glands
Secretions of this gland are released from the cell in secretory vesicles via exocytosis; most endocrine glands of the body are merocrine glands.
Apocrine glands
Secretions of this gland come from portions of the cell that are pinched off from the rest of the cell by exocytosis.
Holocrine
Secretions of this gland are created when secretory cells mature and rupture.
Connective tissue
One of the most abundant and widely distributed tissues in the body; tissue consists of two basic elements: extracellular matrix and cells.
Extracellular matrix
The material located between cells. The extracellular matrix consists of protein fibers and ground substance, the material between the cells and the fibers. The structure of the extracellular matrix determines much of the tissue’s qualities.
What is the functional role of connective tissue?
In its various forms, connective tissue has a variety of functions. It binds together, supports, and strengthens other body tissues; protects and insulates internal organs; compartmentalizes structures such as skeletal muscles; serves as the major transport system within the body (blood, a fluid connective tissue); is the primary location of stored energy reserves (adipose, or fat, tissue); and is the main source of immune responses.
Fibroblasts
Are large flat cells that move through connective tissue and secrete fibers and ground substance.
Macrophages
Develop from monocytes and destroy bacteria and cell debris by phagocytosis.
Plasma cells (plasmocytes)
Develop from B lymphocytes. They secrete antibodies that attack and neutralize foreign substances.
Mast cells (mastocytes)
Are abundant along blood vessels. They produce histamine, which dilates small blood vessels during inflammation and kills bacteria.
Adipocytes
Are fat cells that stores fats. They are found below the skin and around the organs (heart, kidney).
Leukocytes
White blood cells; there are two types: eosinophils and neutrophils. Eosinophils migrate to sites of parasitic infection and allergic responses. Neutrophils migrate to sites of infection that destroy microbes by phagocytosis.
Hyaluronic acid
Is a viscous, slippery substance that binds cells together, lubricates joints, and helps maintain the shape of the eyeballs.
What are the three types of fibers?
Collagen fibers, elastic fibers, and reticular fibers.
Collagen fibers
Are very strong and resist pulling or stretching, but they are not stiff, which allows tissue flexibility. The properties of different types of collagen fibers vary from tissue to tissue.
Elastic fibers
Are smaller in diameter than collagen fibers. Because of their unique molecular structure, elastic fibers are strong but can be stretched up to 150% of their relaxed length without breaking. Additionally, elastic fibers have the ability to return to their original shape after being stretched, a property called elasticity.
Reticular fibers
Are much thinner than collagen fibers and form branching networks. Like collagen fibers, reticular fibers provide support and strength. Form the stroma (supporting framework) of many soft organs.
Embryonic connective tissue
Refers to the connective tissue present in an embryo or a fetus. There are two types which include mesenchyme connective tissue and mucous connective tissue.
Mesenchyme connective tissue
Almost exclusively under skin and along developing bones of embryo; forms almost all other types of connective tissue.
Mucous connective tissue
In umbilical cord and fetus; provides support.
Mature connective tissue
Refers to the connective tissue that is present at birth and persists through life.
Connective tissue proper
Is flexible and contains a viscous ground substance with abundant fibers; include loose connective tissue and dense connective tissue.
Loose connective tissue
The fibers of this type of tissue are loosely arranged between cells; includes areolar connective tissue, adipose tissue, and reticular connective tissue.
Dense connective tissue
More fibers in this type of tissue, and the fibers are thicker and more densely packed; have considerably fewer cells than loose connective tissue; includes dense regular connective tissue, dense irregular connective tissue, and elastic connective tissue.
Supporting connective tissue
Protects and supports soft tissues of the body.
Cartilage
Cartilage plays an important role as a support tissue in the body. It is also a precursor to bone, forming almost the entire embryonic skeleton. There are three types of cartilage which include hyaline cartilage, fibrocartilage, and elastic cartilage.
What are the two basic growth patterns of cartilage?
Interstitial growth and appositional growth.
Interstitial growth
There is growth from within the tissue. Occurs while the cartilage is young and pliable, during childhood and adolescence.
Appositional growth
There is growth at the outer surface of the tissue. Starts later than interstitial growth and continues through adolescence.
Chondrocytes
Cells of mature cartilage.
Lucunae
Spaces in the extracellular matrix.
Perichondrium
Dense irregular connective tissues that surround the surface of most cartilage and contains blood vessels and nerves and is the source of new cartilage cells.
Bone tissue
Bones store calcium and phosphorus, house red bone marrow, which produces blood cells, and contain yellow bone marrow, a storage site for triglycerides; bone tissue is classified as either compact or spongy, depending on how its extracellular matrix and cells are organized.
Compact bone tissue
Consists of osteons (haversian systems) that contain lamellae, lucunae, canaliculi, and central (haversian) canals.
Lamellae
Concentric rings of extracellular matrix that consist of mineral salts, which give bone its hardness and compressive strength, and collagen fibers, which give bone its tensile strength. The lamellae are responsible for the compact nature of this type of bone tissue.
Lucunae
Small spaces between lamellae that contain mature bone cells called osteocytes.
Canaliculi
Project from the lucunae; networks of minute canals containing the processes of osteocytes. Canaliculi provide routes for nutrients to reach osteocytes and for wastes to leave them.
Central (haversian) canals
Contains blood vessels and nerves.
Spongy bone tissue
Lack osteons, and instead have columns of bone called trabeculae.
Liquid connective tissue
Has liquid as it’s extracellular matrix; includes blood, blood plasma, and lymph.
Blood
One of the liquid connective tissues; consists of blood plasma and formed elements.
Blood plasma
One of the liquid connective tissues; suspended in the blood plasma are formed elements - red blood cells, white blood cells, and platelets.
Lymph
One of the liquid connective tissues; flows in lymphatic vessels; consists of several types of cells in a clear liquid extracellular matrix that is similar to blood plasma but with much less protein.
Membrane
Flat sheets of pliable tissue that cover or line a part of the body; there are four different types which include: mucous membranes (mucosa), serous membranes, cutaneous membranes, and synovial membranes.
Mucous membranes (mucosa)
Line body cavities that open to the outside.
Serous membranes
Line body cavities that do not open directly to the outside
Cutaneous membranes
Skin that covers the surface of the body; consists of a superficail portion called the epidermis and a deeper portion called the dermis.
Synovial membranes
Line joints; are composed of a discontinuous layer of cells called synoviocytes and a layer of connective tissue; synociocytes secrete some components of synovial fluid.
Synovial fluid
Lubricates and nourishes the cartilage covering the bones at movable joints and contains macrophages that remove microbes and debris from the joint cavity.
Muscular tissue
Consists of elongated cells called muscle fibers or myocytes that can use ATP to generate force. As a result, muscular tissue produces body movements, maintains posture, and generates heat. It also provides protection; there are three different types which include: skeletal muscle tissue, cardiac muscle tissue, and smooth muscle tissue.
Skeletal muscle tissue
Consist of long, cylindrical striated fibers (alternating light and dark bands within fibers); is considered voluntary because it can contract or relax by conscious control; usually attached to bone by tendons; functions include motion, posture, heat production, and protection.
Cardiac muscle tissue
Consist of branched, strained fibers (alternating light and dark bands within fibers); attach end to end by intercalated discs, which contain desomosomes and gap junctions; is considered involuntary because it’s not consciously controlled; found in heart wall; functions to pump blood to all parts of the body.
Smooth muscle tissue
Consists of nonstriated fibers (hence why its smooth); contain a single, centrally located nucleus; is considered involuntary because it’s not consciously controlled; found in iris of eyes, walls of hollow internal structures such as blood vessels, airways to lungs, stomach, intestines, gallbladder, urinary bladder, and uterus; functions include motion (constriction of blood vessels and airways, propulsion of foods through gastrointestinal tract, contractions of urinary bladder and gallbladder).
Nervous tissue
Consists of only two principal types of cells: neurons and neuroglia; exhibits sensitivity to various types of stimuli, converts stimuli into nerve impulses (action potential), and conducts those nerve impulses to other neurons, muscle fibers, or glands.
Neurons
AKA nerve cells; are sensitive to various stimuli. They convert stimuli into electrical signals called nerve action potentials (nerve impulses) and conduct these action potentials to other neurons, muscle tissue, or glands. Most neurons consist of three basic parts: a cell body and two kinds of cell processes: dendrites and axons.
Neuroglia
Do not generate or conduct nerve impulses, but these cells do have many important supportive functions.
Because neurons and muscle fibers exhibit electrical excitability, they are considered ______.
Excitable cells
Electrical excitability
Is the ability to respond to certain stimuli by producing electrical signals such as action potentials.
