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Chapter 4Tissues,

Glands, and Membranes

Simple Columnar Epithelium

Tissues and Histology

• Tissues are collections of similar cells and the extracellular matrix surrounding them

• Histology is the study of tissues

• The four primary tissue types are– Epithelial tissue– Connective tissue– Muscle tissue– Nervous tissue

Embryonic Tissue

• Primary tissue types are derived from the embryonic germ layers– Endoderm

• Forms the lining of the digestive tract and its derivatives

– Mesoderm• Forms tissues such as muscle, bone, and blood

vessels

– Ectoderm• Forms the outermost layer of skin and the nervous

system

• Gives rise to all tissues of the body

Epithelial Tissue

• Epithelial tissue – Covers surfaces– Has little extracellular material– Usually has a basement membrane– Has no blood vessels

• Epithelial cells– Have a free, or apical, surface (not attached to

other cells)– A lateral surface (attached to other cells)– A basal surface (attached to the basement

membrane)

Fig. 4.1

Epithelial Tissue Functions

1. Protecting underlying structures– Example: outer layer of skin and oral mucosa

2. Acting as barriers– Example: outer layer of skin

3. Permitting the passage of substances– Example: epithelium in the lungs

4. Secreting substances– Example: mucous glands and sweat glands

5. Absorbing substances– Example: epithelial cells of the intestine

Epithelial Tissue Classification

• Epithelia are classified according to the number of cell layers and the shape of the cells– Cell layers

• Simple epithelium has one layer of cells• Stratified epithelium has more than one cell layer• Pseudostratified epithelium has one layer, but appears

to have two or more layers• Transitional epithelium is stratified epithelium that can

be greatly stretched

– Cell shape• Squamous are flat and thin• Cuboidal are cubelike• Columnar are tall and thin

Tab. 4.1a

Tab. 4.1b

Tab. 4.1c

Tab. 4.1d

Tab. 4.2a

Tab. 4.2b

Tab. 4.2c

Tab. 4.2d

Epithelial Tissue Structural and Functional Relationships

• Cell Layers and Cell Shapes– Simple epithelium is involved with

• Diffusion• Secretion• Absorption

– Stratified epithelium serves a protective role– Squamous cells function in

• Diffusion• Filtration

– Cuboidal or columnar cells, which contain cellular organelles

• Secrete• Absorb

• Structural and Functional Relationships– Free Cell Surfaces

• A smooth, free surface reduces friction– Example: Lining of blood vessels

• Microvilli are cylindrical extensions of the cell membrane that increase surface area (cells involved in absorption of secretion)– Example: Lining of the small intestines

• Cilia propel materials over the cell surface– Example: Lining of the nasal cavity and trachea

Epithelial Tissue Structural and Functional Relationships

•Cell connections– Tight junctions bind adjacent

cells together and form a permeability barrier

– Desmosomes mechanically bind cells together

– Hemidesmosomes mechanically bind cells to the basement membrane

– Gap junctions allow intercellular communication

Fig. 4.2

Epithelial Tissue Structural and Functional Relationships

Epithelial Tissue Glands

• A gland is a single cell or a multicellular structure that secretes– Endocrine glands do not have ducts

• Secrete hormones directly into the blood

– Exocrine glands have ducts• Secretions are released onto a surface or into

a cavity– Sweat glands and mammary glands

• Classified by– Structure– How products leave the cell

Epithelial Tissue Glands

Fig. 4.3

• Structure of Exocrine Glands– Simple: have one duct– Compound: have ducts that branch repeatedly– Tubules: ducts end in small tubes– Acini: ducts end in saclike structures– Alveoli: ducts end in hollow sacs

Epithelial Tissue Glands

Fig. 4.4

• Exocrine Glands and Secretion Types– Merocrine – no loss of cellular material (Ex. sweat glands)– Apocrine – part of the cell pinches off (Ex. mammary

glands)– Holocrine – entire cell is shed (Ex. sebaceous glands)

Connective Tissue

• Consist of cells seperated from each other by abundant extracellular matrix

• Functions1. Enclosing and separating

2. Connecting tissues to one another (Ex. Ligaments and Tendons)

3. Supporting and moving (Ex. Bones and cartilage)

4. Storing (Ex. Adipose tissue and Bones)

5. Cushioning and insulating (Ex. Adipose tissue)

6. Transporting (Ex. Blood)

7. Protecting (Ex. Blood and Bones)

Connective Tissue Cells

• Specialized cells of various connective tissues produce the extra cellular matrix

– End in suffixes that identify the cell functions• Blast (germ) cells form the matrix• Cyte (cell) cells maintain it• Clast (break) cells break it down

Connective Tissue

• Extracellular matrix contains– Protein fibers

• Collagen fibers are flexible but resist stretching

• Reticular fibers form a fiber network• Elastic fibers recoil

– Ground substance• Proteoglycans in ground substance hold

water, enabling connective tissues to return to their original shape after being compressed

– Fluid

Connective Tissue Classification

• Mesenchyme:– embryonic connective

tissue that gives rise to six major categories of connective tissue

Connective Tissue Classification

• Loose, or areolar, connective tissue is the “loose packing” material of the body– Fills the spaces between organs– Holds organs in place

• Adipose tissue (fat)– Stores energy– Pads and protects parts of the body– Acts as a thermal insulator

• Dense connective tissue consists of a matrix containing densely packed fibers– Collagen fibers (Ex. tendons, ligaments, and dermis of

the skin)– Elastic fibers (Ex. elastic ligaments and in the walls of

arteries)

Connective Tissue Classification

• Cartilage provides support– Hyaline cartilage (Ex. covers ends of bones and forms

costal cartilages)– Fibrocartilage (Ex. disks between vertebrae)– Elastic cartilage (Ex. external ear)

• Bone has a mineralized matrix– forms most of the skeleton of the body

• Compact bone has more matrix than spaces• Cancellous bone has more spaces then matrix

• Blood has a liquid matrix– Found in blood vessels– Produced in hemopoietic tissue (red bone marrow)

Tab. 4.4

Tab. 4.5a

Tab. 4.5b

Tab. 4.5c

Tab. 4.5d

Tab. 4.6a

Tab. 4.6b

Tab. 4.7a

Tab. 4.7b

Tab. 4.7c

Tab. 4.8

Tab. 4.9

Muscle Tissue• Specialized to contract, or shorten, making movement

possible– Length of muscle cells is greater than the diameter– Sometimes called muscle fibers because they often resemble tiny threads

• Three types of muscle tissue– Skeletal

• Meat of animals• Constitutes ~40% of a person’s body weight• Attaches to the skeleton and allows for movement• Voluntary, multinucleated, and striated (banded)

– Cardiac• Muscle of the heart• Connected to one another by intercalated disks (contain gap junctions)• Involuntary, striated, and usually have one nucleus per cell

– Smooth• Forms the walls of hollow organs (except the heart) and also is found

in the skin and the eyes• Involuntary, not striated, and have a single nucleus

Tab. 4.10a

Tab. 4.10b

Tab. 4.10c

Nervous Tissue

• Nervous tissue is specialized to conduct action potentials (electrical signals)

• Neurons conduct action potentials

• Neuroglia support the neurons

Tab. 4.11

Membranes

• Mucous membranes line cavities that open to the outside of the body– Digestive, respiratory, urinary, and reproductive tracts– Contain glands– Secrete mucus

• Serous membranes line trunk cavities that do not open to the outside of the body– pleural, pericardial, and peritoneal cavities– Do Not contain glands– Secrete serous fluid

• Synovial membranes line freely movable joints

Fig. 4.5

Inflammation

• Function of the inflammatory response is to isolate and destroy harmful agents

• Five symptoms– Redness– Heat– Swelling– Pain– Disturbance of function

• Chronic inflammation results when the agent causing injury is not removed or something else interferes with the healing process

Fig. 4.6

Tissue Repair• Tissue repair is the substitution of viable cells for

dead cells– Labile cells divide throughout life and can undergo

regeneration– Stable cells do not ordinarily divide but can

regenerate if necessary– Permanent cells have little or no ability to divide

• If killed, repair is by replacement

• Tissue repair involves– Clot formation– Inflammation– Formation of granulation tissue– Regeneration or replacement of tissues

• In severe wounds, wound contracture can occur

Fig. 4.7

Tissues and Aging

• Cells divide more slowly as people age• Injuries heal more slowly• Extracellular matrix containing collagen

and elastic fibers becomes less flexible and less elastic

• Consequently– Skin wrinkles– Elasticity in arteries is reduced– Bones break more easily