CHAPTER 4 TISSUES. TYPES OF TISSUES TISSUE- groups of cells having similar structure and function...
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Transcript of CHAPTER 4 TISSUES. TYPES OF TISSUES TISSUE- groups of cells having similar structure and function...
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CHAPTER 4CHAPTER 4
TISSUESTISSUES
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TYPES OF TISSUESTYPES OF TISSUESTISSUE- groups of cells having similar
structure and function
RECALL: HISTOLOGY- study of tissues
There are 4 primary kinds of tissues:
EPITHELIAL
CONNECTIVE
NEURAL
MUSCLE
- tissues combine to form organs of the body
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EPITHELIAL TISSUEEPITHELIAL TISSUE
Epithelial tissue includes EPITHELIA and GLANDS
EPITHELIA (UM)- tissues that cover surfaces and line internal structures and cavities of the body
GLANDS- made up of secreting cells derived from epithelia
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CHARACTERISTICS CHARACTERISTICS
- cells are close together
- free surface exposed to environment or some internal passageway
- attached to underlying connective tissue by a BASEMENT MEMBRANE
- are AVASCULAR- having no blood vessels; nutrients must be obtained from deeper tissues or exposed surfaces
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Epithelia cover external and internal body surfaces:
- skin
- lining of digestive, respiratory, reproductive, and urinary tracts
Separates deep tissues from external environment
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Epithelia also line internal cavities and passageways:
- chest cavity
- fluid-filled chambers in brain, eye, and inner ear
- inner surfaces of blood vessels and heart
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FUNCTIONS OF EPITHELIAFUNCTIONS OF EPITHELIA
Four essential functions:
1. Provide physical protection- protects exposed surfaces from abrasion, dehydration, destruction by chemical or biological agents
2. Control permeability- controls substances that enter and leave the body
3. Provide sensation- detect changes in the environment and relay info. to the nervous system
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4. Produce specialized secretions- cells that produce secretions are called GLAND CELLS
- EXOCRINE secretions- discharged onto surface of the skin or other epithelial surface (Ex: perspiration)
- ENDOCRINE secretions- released into surrounding tissue and blood (hormones)
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INTERCELLULAR INTERCELLULAR CONNECTIONSCONNECTIONS
To be an part of an effective barrier, epithelial cells must remain firmly attached to one another
- accomplished by CELL JUNCTIONS
3 TYPES OF JUNCTIONS:
TIGHT JUNCTIONS- cell membranes are fused together
GAP JUNCTIONS- proteins in the membranes bind and create channels between the 2 cells
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DESMOSOMES- cells are attached by protein filaments
Junctions
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SURFACE OF EPITHELIASURFACE OF EPITHELIA
Many epithelia have MICROVILLI- small, finger-shaped projections of the cell membrane
- increase the surface area of the cell
Some epithelial cells have CILIA- long, finger-shaped extensions of the cell membrane
- beat simultaneously to move materials across the epithelial surface
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BASEMENT MEMBRANEBASEMENT MEMBRANE
Epithelial cells also must remained attached to the rest of the body
- BASEMENT MEMBRANE- lies between the epithelium and underlying connective tissues
- consists of a network of protein fibers (no cells)
- it provides strength, resists distortion, and provides a barrier
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CLASSIFYING EPITHELIACLASSIFYING EPITHELIA
Epithelia are classified by the number of cell layers, and the shape of the exposed cells
2 TYPES OF LAYERING:
- Simple
- Stratified
3 CELL SHAPES:
- Squamous
- Cuboidal
- Columnar
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LAYERSLAYERS
SIMPLE EPITHELIUM- single layer of cells covering the basement membrane
- thin
- only found in protected areas in the body- body cavities, interior of heart and blood vessels
STRATIFIED EPITHELIUM- several layers of cells above basement membrane
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- found in areas subject to mechanical or chemical stresses
- surface of skin, linings of mouth and anus
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CELL SHAPECELL SHAPE
1. SQUAMOUS- cells are thin and flat; cells look like fried eggs (due to nuclei) laid side by side
2. CUBOIDAL- cells appear square; nuclei lie near the center of each cell and form a neat row
3. COLUMNAR- also square, but taller and more slender; nuclei crowded into narrow band close to basement membrane
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SIMPLE SQUAMOUS SIMPLE SQUAMOUS EPITHELIAEPITHELIA
- found in protected regions where absorption takes place or where a slick, slippery surface reduces friction
- linings of body cavities; lining of blood vessels and heart
Simple Squamous
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SIMPLE CUBOIDAL SIMPLE CUBOIDAL EPITHELIAEPITHELIA
- provides limited protection and occurs in regions where secretion or absorption takes place
- secrete enzymes and buffers in the pancreas; line portions of kidneys involved in production of urine
Simple Cuboidal
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SIMPLE COLUMNAR SIMPLE COLUMNAR EPITHELIAEPITHELIA
- provides some protection and may also occur in areas of absorption or secretion
- lines the stomach, intestinal tract, and many excretory ducts
Simple Columnar
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PSEUDOSTRATIFIED PSEUDOSTRATIFIED EPITHELIAEPITHELIA
- columnar epithelia that appears layered because nuclei are situated at varying distances from the surface, but is not actually layered
- typically has cilia
- lines nasal cavity, trachea, bronchi, portions of male reproductive tract
Pseudostratified Ciliated
Stratified Columnar Ciliated
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STRATIFIED SQUAMOUS STRATIFIED SQUAMOUS EPITHELIAEPITHELIA
- found where mechanical stresses are severe
- surface of skin, lining of mouth, tongue, esophagus, and anus
Stratified Squamous
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CONNECTIVE TISSUECONNECTIVE TISSUE
- most diverse tissues of the body
All have 3 basic components:
1. Specialized cells
2. Protein fibers
3. Ground substance- a fluid that varies in consistency
- 2 and 3 make up the MATRIX that surrounds the cells
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- connective tissues are made up mostly of this matrix
- never exposed to outside environment
FUNCTIONS:
- Support and protection
- Transport of materials
- Storage of energy reserves- fats
- Defense of the body- production of antibodies
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CLASSIFYING CONNECTIVE CLASSIFYING CONNECTIVE TISSUESTISSUES
3 classes of connective tissue based on the physical properties of their matrix:
1. CONNECTIVE TISSUE PROPER- has many types of cells and fibers surrounded by a syrupy ground substance
- tissues underlying the skin, fatty tissue, tendons, and ligaments
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2. FLUID CONNECTIVE TISSUES- have distinctive population of cells suspended in a watery ground substance containing dissolved proteins
- blood and lymph
3. SUPPORTING CONNECTIVE TISSUES- cartilage and bone
- less diverse cell population, dense matrix
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CONNECTIVE TISSUE CONNECTIVE TISSUE PROPERPROPER
CELL TYPES:
1. FIBROBLASTS- most abundant; produce and maintain connective tissue fibers and the ground substance
2. MACROPHAGES- engulf damaged cells or pathogens
3. FAT CELLS- adipose cells; number varies from one connective tissue to another
4. MAST CELLS- contain chemicals that are released in times of defense
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- WHITE BLOOD CELLS- produce ANTIBODIES when tissue is damaged
3 TYPES OF FIBERS IN CONNECTIVE TISSUE:
1. COLLAGEN FIBERS- long, straight, unbranched; most common; strong; flexible
2. ELASTIC FIBERS- contain protein elastin; branched and wavy; after stretching will return to original length
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3. RETICULAR FIBERS- least common; thinner than collagen; form branching, interwoven network in organs
GROUND SUBSTANCE
- fills space between cells and surrounds connective tissue fibers
- normally clear, colorless, similar in consistency to maple syrup
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CONNECTIVE TISSUE PROPER:CONNECTIVE TISSUE PROPER:
LOOSE CONNECTIVE TISSUELOOSE CONNECTIVE TISSUE- least specialized connective tissue in body
- contains all cells and fibers in connective tissue proper
- forms a layer that separates the skin from underlying muscles
- provides padding
Loose Connective
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CONNECTIVE TISSUE PROPER:CONNECTIVE TISSUE PROPER:
ADIPOSEADIPOSE TISSUETISSUE- FAT
- loose connective tissue containing large numbers of fat cells
- loose connective tissue becomes adipose tissue when it is dominated by FAT CELLS
- more padding; shock absorption; insulation; energy storage
- skin of sides, buttocks; fills sockets behind eyes
Adipose
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CONNECTIVE TISSUE PROPER:CONNECTIVE TISSUE PROPER:
DENSE CONNECTIVE TISSUEDENSE CONNECTIVE TISSUE- consists mostly of collagen fibers
TENDONS- cords of dense connective tissue that attach skeletal muscles to bones
LIGAMENTS- bundles of fibers that connect one bone to another
- contain elastic fibers and collagen fibers (stretchy)
Tendon
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FLUID CONNECTIVE TISSUE:FLUID CONNECTIVE TISSUE:
BLOOD AND LYMPHBLOOD AND LYMPHBLOOD and LYMPH contain distinct collections
of cells in a fluid matrix
- RED BLOOD CELLS- account for more than ½ the volume of blood; transport oxygen
- PLASMA- watery matrix of blood
- WHITE BLOOD CELLS- important components of immune system
- PLATELETS- cell fragments that function in blood clotting
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SUPPORTING CONNECTIVE TISSUE:SUPPORTING CONNECTIVE TISSUE:
CARTILAGE AND BONECARTILAGE AND BONE
- provide strong framework that supports the rest of the body
CARTILAGE
- firm gel containing embedded fibers
- only cells found within the matrix are CHONDROCYTES, which live in small pockets called lacunae
- cartilage is avascular
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SUPPORTING CONNECTIVE TISSUE:SUPPORTING CONNECTIVE TISSUE:
CARTILAGECARTILAGE
There are 3 major types of cartilage:
1. HYALINE CARTILAGE- most common
- tough and somewhat flexible
- connects ribs to sternum, covers surfaces of bones within joints
2. ELASTIC CARTILAGE- contains numerous elastic fibers that make it very flexible and resilient
- outer ear, epiglottis (covering of larynx)
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3. FIBROCARTILAGE- has little ground substance; dominated by collagen fibers
- extremely durable and tough
- between vertebrae of spinal column- resist compression, absorb shock
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SUPPORTING CONNECTIVE TISSUE:SUPPORTING CONNECTIVE TISSUE:
BONEBONE- also called OSSEOUS TISSUE
- volume of ground substance compared to cartilage is very small
- matrix consists mainly of hard calcium compounds and flexible collagen fibers
- lacunae within the matrix contain bone cells, called OSTEOCYTES
- each bone is surrounded by a PERIOSTEUM- covering made of fibrous and cellular layers
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Bone is constantly being remodeled throughout life
- complete repairs can be made even after severe damage
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MUSCLE TISSUEMUSCLE TISSUE
Muscle tissue is specialized for contraction
- muscle cell contraction involves interactions between filaments of MYOSIN and ACTIN, which are proteins found in the cytoskeletons of cells
There are 3 main types of muscle tissue:
1. Skeletal
2. Cardiac
3. Smooth
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MUSCLE TISSUEMUSCLE TISSUE::SKELETAL MUSCLE TISSUESKELETAL MUSCLE TISSUE
- contains very large, multinucleated cells
- skeletal muscles are long and slender, so are usually called MUSCLE FIBERS
- these fibers are not capable of dividing, but new ones are produced through the division of stem cells in muscle tissue some repair is possible after an injury
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MUSCLE TISSUEMUSCLE TISSUE::SKELETAL MUSCLE TISSUESKELETAL MUSCLE TISSUE
- because of how actin and myosin filaments are arranged, skeletal muscle appears to have a series of bands called STRIATIONS
- skeletal muscle is described as STRIATED VOLUNTARY MUSCLE because the nervous system provides voluntary control over its activities
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MUSCLE TISSUEMUSCLE TISSUE::CARDIAC MUSCLE TISSUECARDIAC MUSCLE TISSUE
- found only in the heart
- cells are much smaller than skeletal muscle fibers, and each cell usually has a single nucleus
- also have striations
- cardiac muscle cells are interconnected at INTERCALATED DISCS, special attachment sites that have gap junctions and desmosomes
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- cells of cardiac muscle cannot divide; tissue cannot regenerate
- cardiac muscle cells do not rely on nerve activity to start a contraction; called STRIATED INVOLUNTARY MUSCLE
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MUSCLE TISSUEMUSCLE TISSUE::SMOOTH MUSCLE TISSUESMOOTH MUSCLE TISSUE
- found in the walls of blood vessels, around hollow organs (urinary bladder), in layers around respiratory, circulatory, digestive, and reproductive tracts
- cells are small and slender, tapering to a point at each end; each has one nucleus
- actin and myosin filaments are scattered, so there are no striations
- cells can divide, so smooth muscle can regenerate after an injury
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- nervous system does not provide voluntary control, so smooth muscle is known as NONSTRIATED INVOLUNTARY MUSCLE
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Neural TissueNeural Tissue
- also known as nerve tissue; is specialized for the conduction of electrical impulses from one part of the body to another
- most of this tissue is concentrated in the brain and spinal cord
CONTAINS 2 TYPES OF CELLS:
1. NEURONS- control conscious and unconscious thought processes
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2. NEUROGLIA- provide physical support for neural tissue, maintain the chemical composition of the tissue fluids, defend the tissue from infection
STRUCTURE OF A NEURON
- neurons are the longest cells in your body (up to 1 m in length)
- limited ability to repair because are unable to divide
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- a typical neuron has a CELL BODY with a large nucleus
- extending from the body are several branches called DENDRITES and one AXON
- DENDRITES receive information from other neurons and AXONS carry that information to other cells
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TISSUE INJURY AND REPAIRTISSUE INJURY AND REPAIR
Tissue repair involves 2 related processes:
1. INFLAMMATION
- the injured area is isolated from neighboring healthy tissue while damaged cells, tissue components, and dangerous microorganisms are cleaned up
- produces swelling, warmth, redness, and pain
INFECTION- inflammation resulting from presence of bacteria
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2. REGENERATION
- damaged tissues are replaced or repaired to restore normal functioning
- fibroblasts produce a network of collagen fibers called SCAR TISSUE
- over time this scar tissue resumes a more normal appearance
- regeneration is most successful in epithelia and connective tissue
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AGINGAGING
- there is a decrease in the speed and effectiveness of tissue repair
- epithelia get thinner; connective tissue gets more fragile
- individuals bruise more easily; bones become brittle
- cancer rates also increase with age