40 terms

Ch 4. Tissue

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Tissue
Groups of cells that are similar in structure and perform a common or related function.

Components:
1. Cells- named by their function and morphology

2. Matrix -the product secreted by and surrounding the cell. Some tissues are mostly cells and have very little matrix; others are mostly matrix with very little cells.
Four Types of Tissue
A. Epithelial
B. Connective
C. Muscular (Muscle)
D. Neural (Nervous)
Epithelium
Sheet of cells that covers a body surface or lines a body cavity. It occurs in the body as (1) covering and lining epithelium and (2) glandular epithelium (forms glands).

Characteristics:
.Primarily cells, very little matrix.
.Has polarity.
.Avascular.
.High mitotic rate (regeneration).


Epithelial functions include protection, absorption, filtration, excretion, secretion and sensory reception.
Simple Squamous Epithelium
Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm.

Function: allows materials to pass by diffusion and filtration in sites where protection is not important; secretes lubricating substances in.

Location: Kidney glomeruli; air sacs of lungs; lining of the heart, blood vessels and lymphatic vessels; lining of ventral body cavity (serosae).
Simple Cuboidal Epithelium
Description: Single layer of cubelike cells with large, spherical central nuclei. Forms ducts.

Function: Secretion and absorption

Location: Kidney tubules; ducts and secretory portions of small glands, ovary surface.
Simple Columnar Epithelium
Description: Single layer of long, narrow cells with large round to oval nuclei; many cells bear microvilli, some bear cilia; layer may contain mucus secreting unicellular glands (goblet cells).

Function: Absorption; secretion of mucus, enzymes and other substances; ciliated type propel mucus (or reproductive cells) by ciliary action.

Location: Nonciliaed type lines most of the digestive track (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.
Pseudostratified Columnar Epithelium
Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia.

Function: Secrete substances particularly mucus; propulsion of mucus by ciliary action.

Location: Nonciliated type in males' sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory track.
Stratified Squamous Epithelium
Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.

Function: Protects underlying tissues in areas subjected to abrasion.

Location: Nonkeratinized type forms the moist lining of the esophagus, mouth, and vagina, keratinized variety form the epidermis of the skin.
Stratified Cuboidal Epithelium
Description: Generally two layers of cubelike cells.

Function: Protection

Location: Large ducts of sweat glands, mammary glands, and salivary glands.
Stratified Columnar Epithelium
Description: Several cell layers; basal cells usually cuboidal; superficial cells elongated and columnar.

Function: Protection; secretion.

Location: Rare in the body; small amount sin male urethra and in large ducts of some glands.
Transitional Epithelium
Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch.

Function: Stretches readily and permits distension of urinary organ by contained urine.

Location: Lines the ureters, urinary bladder, and part of the urethra.
Glands
A gland consists of one or more cells that make and secrete a particular product.

Unicellular glands are scattered within epithelial sheets. By contrast most multicellular epithelial glands form by invagination (inward growth) of an epithelial sheet into the underlying connective tissue.
Endocrine Glands
Often called ductless glands because they lose their surface connection as they develop. They produce hormones, messenger chemicals that they secrete by exocytosis directly into the extracellular space. From there hormones enter the blood or the lymphatic vessels that weave through the glands.
Exocrine Glands
retain their ducts, and their secretions empty through these ducts either to the body surface or into body cavities. Exocrine glands include the sweat and oil glands, liver and pancreas.
Modes of Secretion of Exocrine Glands
1. Merocrine = secrete their products by exocytosis. Cells are not altered.
2. Holocrine= accumulate thier products within themselves until they rupture- die for their cause
3. Apocrine=accumulate product just beneath the free surface, eventually apex of the cell pinches off and releases secretory granules and small amount of cytoplasm. Cell then repairs.
Connective Tissue
Is found in all parts of the body as discrete structures or as part of various body organs. It is the most abundant and widely distributed of the tissue types.

Characteristics: Relatively few cells, Large amount of Matrix. Matrix varies by cell types-bone matrix is solid because of the presence of calcium and phosphate.

Its primary function is to protect, support and bind together other tissues of the body.

For Example, bones are composed of connective tissue and they protect and support other body tissues and organs. The ligaments and tendons (dense connective tissue) bind the bones together or bind skeletal muscles to bones.
Connective Tissue Proper: loose Areolar
Description: Gel-like matrix with all three fiber types (collagen, elastic, reticular); cells: fibroblasts, macrophages, mast cells and some white blood cells.

Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays and important role in inflammation; holds and conveys tissue fluid.

Location: Widely distributed under epithelia of body, e.g. form lamina propia or mucous membranes; packages organs; surrounds capillaries.
Matrix Types
1) Ground substance composed of interstitial fluid, cell adhesion proteins and proteoglycans.
2)Fibers-all proteins
a) Collagen -tough and flexible, resist stretching (
tendons and ligaments)
b) Elastin- Can stretch and recoil (like rubber band)
c) Reticular; thin collagen fiber, form framework for
lymph nodes and spleen.
Connective Tissue Proper: loose adipose
Description: Matrix as in areolar, but very sparse; closely packaged adipocytes or fat cells, have nucleus pushed to the side by large fat droplet.

Function: Provides reserve fuel; insulates against heat loss; supports and protects organs.

Location: Under skin; around kidneys and eyeballs; within abdomen; in breast.
Connective Tissue Proper: loose reticular
Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network.

Function: Fibers form a soft internal skeleton (stroma) that supports other cell types, including white blood cells, mast cells, and macrophages.

Location: Lymphoid organs (lymph nodes, bone marrow, and spleen).
Connective Tissue Proper: dense regular
Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast.

Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction.

Location: Tendons, most ligaments, aponeuroses.
Connective Tissue Proper: dense elastic
Description: Dense regular connective tissue containing a high proportion of elastic fibers.

Function: Allows recoil of tissue following stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following aspiration.

Location: Walls of large arteries within certain ligaments associated with the vertebral column; within he walls of bronchial tubes.
Connective Tissue Proper: dense irregular
Description: Primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast.

Function: Able to withstand tension exerted in many directions; provides structural strength.

Location: Fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract.
Cartilage; Hyaline
Description: Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae.

Function: Supports and reinforces; serves as resilient cushion; resists compressive stress.

Location: Forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx.
Cartilage: elastic
Description: Similar to hyaline cartilage, but more elastic fibers in matrix.

Function: Maintains the shape of a structure while allowing great flexibility.

Location: Supports the external ear (auricle); epiglottis.
Cartilage: fibrocartilage
Description: Matrix similar to but less firm that that in hyaline cartilage; thick collagen fibers predominate.

Function: Tensile strength with the ability to absorb compressive shock.

Location: Intervertebral discs; pubic symphysis; discs of knee joint.
Bones (Osseous Tissue)
Description: Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized.

Function: Bone supports and protects(by enclosing); provides lavers for the muscles to act on; stores calcium and other minerals and fat; marrow inside the bones is the site for blood cell formation (hematopoiesis).

Location: Bones
Blood
Description: Red and white cells in a fluid matrix (plasma).

Function: Transport of respiratory gases, nutrients, wastes, and other substances.

Location: Contained within blood vessels.
Nervous Tissue
Description: Neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body ; also contributing to nervous tissue are nonexcitable supporting cells.

Function: Neurons transmit electrical signals from sensory receptors and to effectors (muscles and glands); supporting cells support and protect neurons.
Muscle Tissue
Muscle tissues are highly cellular, well-vascularized tissues that are responsible for most types of body movement.
Skeletal Muscle
Description: Long, cylindrical, multinucleate cells; obvious striations.

Function: Voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control.

Location: In skeletal muscles attached to bones or occasionally to skin.
Cardiac Muscle
Description: Branching, striated, generally uninucleate cells that interdigitate at specialized junctions called intercalated discs.

Functions: As it contracts, it propels blood into circulation; involuntary control.

Location: The walls of the heart.
Smooth Muscle
Description: Spindle-shaped cells with central nuclei; no striations; cells arranged closely to form sheets.

Function: Propels substances or objects (foodstuff, urine, a baby) along internal passageways; involuntary control.

Location: Mostly in the walls of hollow organs. e. g. Urinary bladder, uterus
Nervous Tissue
is the main component of the nervous system-the brain, spinal cord, and nerves- which regulates and controls body functions. It contains two major cell types: neurons and supporting cells (neuroglials).
Epithelial Membranes
Continuous multicellular sheets composed of at least two primary tissue types; an epithelium bound to an underlying layer of connective tissue proper. Hence these membranes are simple organs.

Classified in 3 types

1. Cutaneous
2. Mucous
3. Serous
Cutaneous Membrane
Is our skin. Organ system consisting of keratinized stratified squamous epithelium (epidermis) firmly attached to a thick layer of connective tissue (dermis). It is a dry membrane, which unlike other epithelial membranes, is exposed to the air.
Mucous Membrane
Line all body cavities that open to the outside of the body, such as the hollow organs of the digestive, respiratory, and urogenital tracks. In all cases, they are wet or moist membranes bathed by secretions, or, in the case of the urinary mucosa urine.

Mucosa refers to location of the membrane, not its cell composition.
Most mucosae contain either stratified squamous or simple columnar epithelia.
Serous Membranes
Moist membranes found in closed ventral cavities. Consists of simple squamous epithelium (mesothelium) resting on a thin layer of loose connective (areolar) tissue.

They secrete a thin lubricant fluid that allows organs to slide across each other easily.
They are named according to their location and specific organ associations.
Two types (parietal and visceral)
Tissue Regeneration
replaces destroyed tissue with the same kind of tissue. Restore normal organ function.
Fibrosis
Replacement with scar tissue. Scar tissue helps to hold organ together, but it does not restore normal function.
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