Chapter 4 - Tissue: The Living Fabric

Define Tissue

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

• Individual body cells are specialized

• Each type performs specific functions that maintain homeostasis

List the four basic tissue types

1. Epithelial tissue ⇒ Forms boundaries between different environments, protects, secretes, absorbs, filters

2. Connective tissue ⇒ Supports protects, binds other tissues together

3. Muscle tissue ⇒ Contracts to cause movement

4. Nervous tissue ⇒ Internal communication

Examples of the four basic tissue types

1. Epithelial tissue

   • Lining of digestive tract organs and other hollow organs

   • Glands (EX: pancreas)

   • Skin surface( epidermis)

2. Connective tissue

   • Bones

   • Tendons

   • Fat and other soft padding tissue

3. Muscle tissue

   • Skeletal → Muscles attached to the bones

   • Cardiac → Muscles of heart

   • Smooth → Muscles of walls of hallow

4. Nervous tissue

   • Brain

   • Spinal cord

   • Nerves

Define Epithelial Tissue

• A a layer of cells that covers body surfaces or cavities

• Forms boundaries between different environments, protects, secretes, absorbs, and filters

List the functions of Epithelial Tissue

1. Protection

2. Absorption

3. Filtration

4. Excretion

5. Secretion

6. Sensory reception

List the special distinguishing characteristics epithelial tissue

1. Protective/secretory/absorptive lining

2. Apical surface - “Free surface”

   • Polarity

3. Basement membrane

   • Support from connective tissue

4. Tightly packed

   • Specialized contacts

5. Avascular

   • Avascularity

6. Basal cells readily divide

   • High regenerative capacity

Explain what it means that Epithelial tissue has is Protective/secretory/absorptive lining

• Protective → Basal surface ⇒ the surface near the base or interior of a structure; nearest the lower side or bottom of a structure

  • Basal lamina → Noncellular, adhesive supporting sheet consisting largely of glycoproteins secreted by epithelial cells; acts as a selective filter that determines which molecules diffusing from the underlying connective tissue are allowed to enter the epithelium & also acts as scaffolding along which epithelial cells can migrate to repair a wound

• Absorptive lining → Apical surface ⇒ the surface that faces the outside of the body or the inner cavity of an organ

  • Microvilli → tiny projections on the free surfaces of some epithelial cells; increase surface area for absorption

  • Cilia → Tiny, hairlike projections of a cell; may move in a wavelike manner to propel substances across the exposed cell surface

Explain what it means that Epithelial tissue has an Apical Surface

Polarity → epithelia have two surfaces that differ in structure and function:

1. Apical surface ⇒ the surface that faces the outside of the body or the inner cavity of an organ

   • Microvilli → tiny projections on the free surfaces of some epithelial cells; increase surface area for absorption

   • Cilia → Tiny, hairlike projections of a cell; may move in a wavelike manner to propel substances across the exposed cell surface

2. Basal surface ⇒ the surface near the base or interior of a structure; nearest the lower side or bottom of a structure

   • Basal lamina → Noncellular, adhesive supporting sheet consisting largely of glycoproteins secreted by epithelial cells; acts as a selective filter that determines which molecules diffusing from the underlying connective tissue are allowed to enter the epithelium & also acts as scaffolding along which epithelial cells can migrate to repair a wound

Explain what it means that Epithelial tissue has a Basement membrane

Support from connective tissue → In between the epithelial and connective tissues is a basement membrane that reinforces the epithelial sheet; helps it resist stretching and tearing, and defines the epithelial boundary; consists of two layers:

1. Basal lamina ⇒ Noncellular, adhesive supporting sheet consisting largely of glycoproteins secreted by epithelial cells; acts as a selective filter that determines which molecules diffusing from the underlying connective tissue are allowed to enter the epithelium & also acts as scaffolding along which epithelial cells can migrate to repair a wound

2. Retricular lamina ⇒ A layer of extracellular material containing a fine network of collagen fibers; together with the basal lamina, it is a major component of the basement membrane

Explain what it means that Epithelial tissue is Tightly packed

Specialized contacts → epithelial cells fit closely together to form continuous sheets; adjacent cells are tied together by:

1. Tight junctions ⇒ Prevent substances from leaking through spaces between cells

2. Desmosomes ⇒ Keep cells from pulling apart

Explain what it means that Epithelial tissue is Avascular

Avascularity → Contains no blood vessels; It is innervated → supplied by nerve fibers

• Epithelial cells are nourished by substances diffusing from blood vessels in the underlying connective tissue

Explain what it means that Epithelial tissue has Basal cells readily divide

Epithelium has a high regenerative capacity

1. If and when their apical-basal polarity and lateral contacts are destroyed, epithelial cells begin to reproduce themselves rapidly

2. As long as epithelial cells receive adequate nutrition, they can replace lost cells by cell division

List two forms of Epithelial tissue that occur in the body

1. Covering and lining epithelium

   • Which forms the outer layer of the skin; dips into and lines the open cavities of the urogenital, digestive, and respiratory systems; and covers the walls and organs of the closed ventral body cavity

2. Glandular epithelium

   • Which forms the glands of the body

Classification of Epithelia based on number of cell layers

1. Simple epithelia

   • Consists of a single cell layer

   • They are typically found where a thin epithelial barrier is desirable

2. Stratified epithelia

   • Composed of two or more cell layers stacked on top of each other

   • Are common in high-abrasion areas where protection is important,

   • EX: skin surface and the lining of the mouth

Classification of Epithelia based on cell shape

1. Squamous cells

   • Flattened and scale-like

2. Cuboidal cells

   • Boxlike, approximately as tall as they are wide.

3. Columar cells

   • Tall and column shaped

Name, classify, and describe the various type of epithelia, and indicate their chief function(s) and location(s)

1. Simple Squamous

2. Simple Cuboidal

3. Simple Columnar

4. Pseudo-stratified Columnar

5. Stratified Squamous

6. Transitional

Indicate their chief function(s) and location(s) of Simple Squamous

• DESCRIPTION: A single layer of squamous cells

• FUNCTION: Highly adapted for filtration and exchange of substances, it forms walls of air sacs of the lungs and lines blood vessels

• LOCATION: It contributes to serosae as mesothelium and lines all hollow circulatory system organs as endothelium

Indicate their chief function(s) and location(s) of Simple Cuboidal

FUNCTION & LOCATION: Commonly active in secretion and absorption, is found in glands and in kidney tubules

Indicate their chief function(s) and location(s) of Simple Columnar

• DESCRIPTION: Consists of a single layer of tall columnar cells that exhibit microvilli and often mucus-producing cells

• FUNCTION: Specialized for secretion and absorption

• LOCATION: It lines most of the digestive tract

Indicate their chief function(s) and location(s) of Pseudo-stratified Columnar

• DESCRIPTION: A simple columnar epithelium that appears stratified

• FUNCTION & LOCATION: Its ciliated variety, rich in mucus-secreting cells, lines most of the upper respiratory passage

Indicate their chief function(s) and location(s) of Stratified Squamous

• DESCRIPTION: Multilayered; cells at the free surface are squamous

• FUNCTION: It is adapted to resist abrasion

• LOCATION: It lines the esophagus and vagina; its keratinized variety forms the skin epidermis

Indicate their chief function(s) and location(s) of Transitional

• DESCRIPTION: A modified stratified squamous epithelium

• FUNCTION: Adapted for responding to stretch

• LOCATION: It lines hollow urinary system organs

Indicate their chief function(s) and location(s) of Stratified Cuboidal

• DESCRIPTION: Typically has two layers of cuboidal cells

• LOCATION: Quite rare in the body, mostly found in the ducts of some of the larger glands (sweat glands, mammary glands)

Indicate their chief function(s) and location(s) of Stratified Columnar

• DESCRIPTION: Only its apical layer of cells is columnar

• FUNCTION: Occurs at transition areas or junctions between two other types of epithelia

• LOCATION: Small amounts are found in the pharynx (throat), the male urethra, and lining some glandular ducts

Define Connective Tissue

• A primary tissue

• Form and function vary extensively

• Functions include binding and support, protection, insulation, fat storage, and transportation (blood)

List the four main classes of Connective Tissue

1. Connective Tissue proper

2. Cartilage

3. Bone

4. Blood

List the Proper Connective Tissues

1. Areolar

2. Adipose

3. Reticular

4. Dense

List the Specialized Connective Tissues

1. Cartilage (supportive connective tissue)

2. Bone (supportive connective tissue)

3. Blood (Fluid CT)

Indicate differences between Connective Tissue

Depending on type, connective tissue may be well vascularized (most), poorly vascularized (dense connective tissue), or avascular (cartilage)

List and describe connective tissue its structural elements

1. Ground substance

   • The unstructured material that fills the space between the cells and surrounds the fibers

     • Gel-like

     • Firm

2. Fibers

   • Proteins that provide support

     • Collagen

     • Elastic

     • Reticular

3. Cells

   • Each major class of connective tissue has a resident cell type that exists in immature (-blast) and mature (-cyte) forms

     • Matrix-secreting cell (-blast)

     • Mature cell (-cyte)

     • Undifferentiated cell type

Ground substance + Fibers = Extracellular matrix

List and describe the three components of Ground Substance

1. Hyaluronic Acid

   • Lubricant

   • Functions as a molecular sieve through which nutrients and other dissolved substances can diffuse between the blood capillaries and the cells

2. Proteoglycans

   • Trap water

   • Consist of a protein core to which large polysaccharides called glycosaminoglycans (GAGs) are attached

   • Tend to form huge aggregates in which the GAGs intertwine and trap water, forming a substance that varies from a fluid to a viscous gel → higher the GAG content, the more viscous the ground substance

3. Adhesive molecules

   • Glue molecules

   • Serve mainly as a connective tissue glue that allows connective tissue cells to attach to the extracellular matrix

List and describe the three types of Connective Tissue Fibers

1. Collage Fibers

   • Fibrous protein → collagen

   • “White fibers” → Assemble spontaneously into cross-linked fibrils

   • Tensile strength

2. Elastic Fibers

   • Rubbery protein → elastin

   • “Yellow fibers” → Long, thin, elastic fibers form branching networks in the extracellular matrix

   • Elasticity

   • EX: skin, lungs, and blood vessel walls

3. Reticular Fibers

   • Short, fine fibers are made of a different type of collagen than the more common, thicker collagen fibers

   • They connect to the coarser collagen fibers, but they branch extensively, forming delicate networks

   • Abundant where connective tissue is next to other tissue types

   • EX: basement membrane of epithelial tissues and around capillaries

List the types of Cells in Connective Tissues

1. -blast ⇒ form new matrix

   • Immature

2. -cytes ⇒ maintain matrix

   • Mature

3. -clasts ⇒ break down matrix

List the two subclasses of Connective Tissue Proper

1. Loose Connective Tissue

   • Areolar

   • Adipose

   • Reticular

2. Dense Connective Tissue

   • Regular

   • Irregular

   • Elastic

Describe Areolar Tissue

Loose Connective Tissue

1. Cells

   • Fibroblasts/cytes

2. Fibers

   • Loose network of mixed fibers

   • Gel-like ground substance

3. Function

   • Binds epithelial tissue to underlying structure, binds muscles together

   • Supporting and binding other tissues (the job of the fibers)

   • Holding body fluids (the ground substance’s role)

   • Defending against infection (via the activity of white blood cells and macrophages)

   • Storing nutrients as fat in adipocytes (fat cells)

4. Location

   • Beneath epithelial tissues

   • Between muscles

Describe Adipose Tissue

Loose Connective Tissue

• Cells

  • Adipocytes

• Fibers

  • Few collagenous

  • Scant matrix

• Function

  • Cushing

  • Insulation

  • Energy storage

• Location

  • Under skin

  • Around vital organs

  • Behind eyes

Describe Reticular

Loose Connective Tissue

1. Cells

   • Fibroblasts/cytes

2. Fibers

   • Reticular → Collagen-based, but much thinner and not as strong

   • Soft ground substance

3. Function

   • Framework for lymphatic structures

4. Location

   • Liver

   • Spleen

   • Lymph nodes

Describe Dense Connective Tissue

1. Cells

   • Fibroblasts/cytes

2. Fibers

   • Both, but one predominates

3. Function

   • Binds body parts together

Describe Regular

Dense Connective Tissue

• DESCRIPTION: dense parallel bundles of collagen fibers; few cells, little ground substance

• FUNCTION: high tensile strength

• LOCATION: forms tendons, ligaments, aponeuroses; in cases where this tissue also contains numerous elastic fibers it is called elastic connective tissue

Describe Irregular

Dense Connective Tissue

• DESCRIPTION: Like regular variety, but fibers are arranged in different planes

• FUNCTION: Resists tension exerted from many different directions

• LOCATION: Forms the dermis of the skin and organ capsules

Describe Elastic

Dense Connective Tissue

Describe Cartilage

Connective Tissue

1. Cells

   • Chondrocytes (-blast, clasts)

2. Matrix

   • Fibers → Collagenous or elastic

   • ground substances → Chondromucoprotein (rigid…semisolid)

List the 3 types of Cartilage

1. Hyaline

2. Elastic

3. Fibrocartilage

Describe Hyaline Cartilage

Cartilage

• DESCRIPTION: Firm ground substance containing collagen fibers

• FUNCTION: Resists compression well

• LOCATION: Found in embryonic skeleton, at articulating surfaces of bones, costal cartilages, and in the trachea; most abundant type

Describe Elastic Cartilage

Cartilage

• DESCRIPTION: Elastic fibers predominate

• FUNCTION: Framework for ears; provides flexible support of the external ear and epiglottis

Describe Fibrocartilage

Cartilage

• DESCRIPTION: parallel collagen fibers

• FUNCTION: resists both tension and compression well

• LOCATION: forms intervertebral discs and knee cartilages

Describe Bone

Connective Tissue

1. Cells

   • Osteo-

2. Matrix

   • Hydroxyapatite

   • Consists of a hard, collagen-containing matrix embedded with calcium salts

3. LOCATION: Forms the bony skeleton

Describe Blood

Connective Tissue

1. Cells

   • RBC

   • WBS

   • PLTS

2. Matrix

   • Fluid (plasma)

Describe the types of connective tissue found in the body and indicate their characteristic functions

Define Muscle tissues

• Group of body tissues that contract (shorten) to produce local movements or the movement of an entire organism

• Muscle cells possess myofilaments

  • Actin filaments

  • Myosin filaments

List the 3 classes of Muscle Tissue

1. Skeletal muscle

2. Cardiac muscle

3. Smooth muscle

Compare and contrast the structures and body locations of the three types of muscle tissue

1. Skeletal muscle

   • long, cylindrical cells that contain many peripherally located nuclei; obvious striations

   • Attached to the bones of the skeleton

   • VOLUNTARY

2. Cardiac muscle

   • striations

   • Specialized muscle of the heart

   • INVOLUNTARY

3. Smooth muscle

   • Spindle-shaped cells with one centrally located nucleus and no externally visible striations (bands)

   • Found mainly in the walls of hallow organs

   • INVOLUNTARY

Define Nervous Tissue

Main component of the nervous system (the brain, spinal cord, and nerves), which regulates and controls body functions

Describe Neurons

• DESCRIPTION: Branching cells

• FUNCTION: Highly specialized nerve cells that generate and conduct nerve impulses

  • Respond to stimuli (via processes called dendrites)

  • Transmit electrical impulses over substantial distances within the body (via processes called axons)

Indicate the general characteristics of Nervous Tissue