Bio 201 chapter 4 lecture

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A tissue is a group of cells

Common embryonic origin

Function together to carry out specialized activities

Hard (bone), semisolid (fat), or liquid (blood) Histology is the science that deals with the

study of tissues. Pathologist specialized in laboratory studies

of cells and tissue for diagnoses

Epithelial

▪ Covers body surfaces and lines hollow organs, body cavities, duct, and forms glands

Connective

▪ Protects, supports, and binds organs.

▪ Stores energy as fat, provides immunity

Muscular

▪ Generates the physical force needed to make body structures move and generate body heat

Nervous

▪ Detect changes in body and responds by generating nerve impulses

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Contact points between the plasma membranes of tissue cells

5 most common types:

▪ Tight junctions

▪ Adherens junctions

▪ Desmosomes

▪ Hemidesmosomes

▪ Gap junctions

Web-like strands of transmembrane proteins

Fuse cells together

Seal off passageways between adjacent cells

▪ Common in epithelial tissues of the stomach, intestines, and urinary bladder

▪ Help to retard the passage of substances between cells and leaking into the blood or surrounding tissues

Dense layer of proteins called plaque

Resist separation of cells during contractile activities

Located inside of the plasma membrane attached to both membrane proteins and microfilaments of the cytoskeleton

Transmembrane glycoproteins called cadherins insert into the plaque and join cells

In epithelial cells, adhesion belts encircle the cell

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Contain plaque and cadherins that extends into the intercellular space to attach adjacent cells together Desmosome plaque attaches

to intermediate filaments that contain protein keratin

Prevent epidermal cells from separating under tension and cardiac muscles cells from pulling apart during contraction

Resemble half of a desmosome Do not link adjacent cells

but anchor cells to the basement membrane

Contains transmembrane glycoprotein integrin

Integrins attach to intermediate filaments and the protein laminin present in the basement membrane

Connect neighboring cells via tiny fluid-filled tunnels called connexons Contain membrane proteins

called connexins Plasma membranes of gap

junctions are separated by a very narrow intercellular gap (space) ▪ Communication of cells

within a tissue ▪ Ions, nutrients, waste,

chemical and electrical signals travel through the connexons from one cell to another

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Epithelial tissue consists of cells arranged in continuous sheets, in either single or multiple layers Closely packed and held tightly together

Covering and lining of the body

Free surface

3 major functions: Selective barrier that regulates the movement of materials in

and out of the body

Secretory surfaces that release products onto the free surface

Protective surfaces against the environment

Surfaces of epithelial cells differ in structure and have specialized functions

Apical (free) surface

▪ Faces the body surface, body cavity, lumen, or duct

Lateral surfaces

▪ Faces adjacent cells

Basal surface

▪ Opposite of apical layer and adhere to extracellular materials

Basement membrane

Thin double extracellular layer that serves as the point of attachment and support for overlying epithelial tissue

Basal lamina

▪ Closer to and secreted by the epithelial cells

▪ Contains laminin, collagen, glycoproteins, and proteoglycans

Reticular lamina

▪ Closer to the underlying connective tissue

▪ Contains collagen secreted by the connective tissue cells

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Own nerve supply

Avascular or lacks its own blood supply

Blood vessels in the connective tissue bring in nutrients and eliminate waste

High rate of cell division for renew and repair

Numerous roles in the body (i.e. protection and filtration)

Covering and lining epithelium ▪ Outer covering of skin and some internal organs

Glandular epithelium ▪ Secreting portion of glands (thyroid, adrenal, and sweat

glands)

Normally classified according to: Arrangement of cells into layers

Shapes of cells

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Arrangement of cells in layers Consist of one or more layers depending on function

Simple epithelium

▪ Single layer of cells that function in diffusion, osmosis, filtration, secretion, or absorption

Pseudostratified epithelium

▪ Appear to have multiple layers because cell nuclei at different levels

▪ All cells do not reach the apical surface

Stratified epithelium

▪ Two or more layers of cells that protect underlying tissues in areas of wear and tear

Cells vary in shape depending on their function

Squamous

▪ Thin cells, arranged like floor tiles

▪ Allows for rapid passage of substances

Cuboidal

▪ As tall as they are wide, shaped like cubes or hexagons

▪ May have microvilli

▪ Function in secretion or absorption

Columnar

▪ Much taller than they are wide, like columns

▪ May have cilia or microvilli

▪ Specialized function for secretion and absorption

Transitional

▪ Cells change shape, transition for flat to cuboidal

▪ Organs such as urinary bladder stretch to larger size and collapse to a smaller size

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Simple squamous epithelium

Simple cuboidal epithelium

Simple columnar epithelium (nonciliated and ciliated)

Pseudostratified columnar epithelium (nonciliated and cilated)

Single layer of cells that resembles a tiled floor on the surface

▪ Nucleus is centrally located and appears flattened oval or sphere

Found at sites for filtration or diffusion

Endothelium

The type of simple squamous that lines the heart, blood vessels, and lymphatic vessels

Mesothelium

The type of epithelial layer of serous membranes such as the pericardium, pleura, or peritoneum

Unlike other epithelial tissue, Both are derived from embryonic mesoderm

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Cuboidal shaped cells

Cell nuclei round and centrally located

Found in thyroid gland and kidneys

Functions in secretion and absorption

Column

shaped cells Oval nuclei at

near base Nonciliated

and ciliated

Contains columnar

cells with microvilli at their apical surface and goblet cells

▪ Secreted mucus serves as lubricant for the lining of digestive, respiratory, reproductive and urinary tracts

▪ Also prevents the destruction of the stomach lining by acidic gastric juices

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Columnar epithelial cells with cilia at the apical surface ▪ In respiratory tract,

goblet cells are interspersed among ciliated columnar epithelia

▪ Secreted mucus on the surface traps inhaled foreign particles. Beating cilia moves particles to the throat for removal by coughing, swallowing, or sneezing

▪ Cilia also moves oocytes to the uterine tubes

Pseudostratified columnar epithelium Appears to have

several layers due to nuclei are various depths

All cells are attached to the basement membrane in a single layer but some do not extend to the apical surface

Ciliated cells secrete mucus and bear cilia

Nonciliated cells lack cilia and goblet cells

Two or more layers of cells Specific kind of stratified epithelium depends

on the shape of cells in the apical layer

Stratified squamous epithelium

Stratified cuboidal epithelium

Stratified columunar epithelium

Transitional epithelium

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Several layers of cells that are flat in the apical layer ▪ New cells are pushed up toward apical layer

▪ As cells move further from the blood supply they dehydrate, harden, and die

Keratinized form contain the fibrous protein keratin ▪ Found in superficial layers of the skin

Nonkeratinized form does not contain keratin ▪ Found in mouth and esophagus

Fairly rare type of epithelium

Apical layers are cuboidal

Functions in protection

Also very uncommon

Columnar cells in apical layer only

Basal layers has shorten, irregular shaped cells

Functions in protection and secretion

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Found only in the urinary system

Variable appearance

In relaxed state, cells appear cuboidal

Upon stretching, cells become flattened and appear squamous

Ideal for hollow structure subjected to expansion

Secretions, called hormones, diffuse directly into the bloodstream

Function in maintaining homeostasis

Secrete products into ducts that empty onto the surfaces of epithelium

Skin surface or lumen of a hollow organ

Secretions of the exocrine gland include mucus, sweat, oil, earwax, saliva, and digestive enzymes

Examples of glands include sudoriferous (sweat) glands

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Most abundant and widely distributed tissues in the body

Numerous functions

Binds tissues together

Supports and strengthen tissue

Protects and insulates internal organs

Compartmentalize and transport

Energy reserves and immune responses

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Extracellular matrix is the material located between the cells

Consist of protein fibers and ground substance

Connective tissue is highly vascular Supplied with nerves

Exception is cartilage and tendon. Both have little or no blood supply and no nerves

Fibroblasts

Secrete fibers and components of ground substance Adipocytes (fat cells)

Store triglycerides (fat) Mast cells

Produce histamine White blood cells

Immune response

Neutrophil and Eosinophils Macrophages

Engulf bacteria and cellular debris by phagocytosis Plasma cells

Secrete antibodies

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Ground substance Between cells and fibers

▪ Fluid, semifluid, gelatinous, or calcified

Functions to support and bind cells, store water, and allow exchange between blood and cells

Complex combination of proteins and polysaccharides

Fibers Collagen fibers

Elastic fibers

Reticular fibers

Embryonic connective tissue Mesenchyme and mucous connective tissue

Mature connective tissue Loose connective tissue

▪ Areolar, adipose, and reticular

Dense connective tissue ▪ Dense regular, dense irregular, and elastic

Cartilage ▪ Hyaline, fibrocartilage, and elastic cartilage

Bone tissue

Liquid connective tissue ▪ Blood and lymph

Mesenchyme

▪ Gives rise to all other connective tissues

Mucous (Wharton’s Jelly)

▪ Found in umbilical cord of the fetus

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Most widely distributed in the body

Contains several types of cells and all three fibers

Contains adipocytes

Good for insulation and energy reserves

White (common) and brown adipose tissue

Fine interlacing reticular fibers and cells

Forms the stroma of liver, spleen, and lymph nodes

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Dense connective tissue

Contains numerous, thicker, and denser fibers

Packed closely with fewer cells than loose connective tissue

Dense regular connective tissue

Bundles of collagen fibers are regularly arranged in parallel patterns for strength

Tendons and most ligaments

Collagen fibers are usually irregularly arranged

Found where pulling forces are exerted in many directions

Dermis of skin and heart

Contain branching elastic fibers

Strong and can recoil to original shape after stretching

Lung tissue and arteries

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Cartilage is a dense network of collagen fibers and elastic fibers firmly embedded in chondroitin sulfate Chrondrocytes ▪ Cartilage cells found in the spaces called lucunae

Pericondrium ▪ Covering of dense irregular connective tissue that

surrounds the cartilage ▪ Two layers: outer fibrous layer and inner cellular layer

No blood vessels or nerves, except pericondrium

Most abundant cartilage in the body

Surrounding by perichondrium (some exceptions like articular cartilage)

Provide flexibility and support. Reduces friction

Chondrocytes are scattered among bundles of collagen fibers within the extracellular matrix

Lack a perichondrium

Strongest type of cartilage

Found in intervertebral disc (between vertebrae)

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Chondrocytes are located within a threadlike network of elastic fibers

Perichondrium is present

Provides strength and elasticity

Cartilage grows slowly When injured or inflamed, repairs is slow due

to its avascular nature. Two patterns of cartilage growth:

Interstitial growth

▪ Growth from within the tissue

Appositional growth

▪ Growth at the outer surface of the tissue

Bones are organs composed of several different connective tissues: bone (osseous) tissue, periosteum, and endosteum.

Compact or spongy Osteon or haversian system

Spongy bone lacks osteons. They have columns called trabeculae

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Blood tissue

Connective tissue with liquid extracellular matrix called blood plasma

Lymph

Mucous membranes Lines a body cavity that

opens directly to the exterior

Epithelial layer is important for the body’s defense against pathogens

Connective tissue layer is areolar connective tissue and is called lamina propria

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Serous membranes or serosa

Lines a body cavity that does not open directly to the exterior. Also covers the organs that lie within the cavity

Consist of areolar connective tissue covered by mesothelium (simple squamous epithelium) that secrete a serous fluid for lubrication

Synovial membranes

Lines joints and contains connective tissue but not epithelium

Consists of elongated cells called muscle fibers or myocytes

Cells use ATP to generate force

Several functions of muscle tissue

Classified into 3 types: skeletal, cardiac, and smooth muscular tissue

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Attached to bones of the skeleton

Have striations

Voluntary movement or contractions by conscious control

Vary in length (up to 40 cm) and are roughly cylindrical in shape

Cardiac muscle tissue Have striations

Involuntary movement or contraction is not consciously controlled

Intercalated disc unique to cardiac muscle tissue

Walls of hollow internal structures

▪ Blood vessels, airways of lungs, stomach, and intestines

Nonstriated

Usually involuntary control

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Consists of two principle types of cells

Neurons or nerve cells

Neuroglia

Neurons and muscle fibers Exhibit electrical excitability

The ability to respond to certain stimuli by producing electrical signals such as action potentials

Actions potentials propagate along a nerve or muscle plasma membrane to cause a response

▪ Release of neurotransmitters

▪ Muscle contraction