4 tissues.pdf

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Chapter 04

Lecture Outline

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Chapter 4-Tissues

• What is a tissue?

group of cells with similar structure and

function plus extracellular substance (matrix)

• Histology:

study of tissues


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Classification of Tissues

• Structure of cells

• Extracellular matrix

• Functions of the cells


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Embryonic Tissue

• Endoderm:

digestive tract

• Mesoderm: muscle,

bone & blood

vessels

• Ectoderm: skin and

nervous system


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Embryonic Tissue


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Types of Tissues

1. Epithelial

2. Connective

3. Muscular

4. Nervous


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Epithelial Tissues

• Location:

- cover body (internal and external)

- Ex. Skin, kidney, trachea, glands, etc.


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• Characteristics:

- cells close together (very little extracellular

matrix)

- form most glands

- have free surface and lateral surface

- Basal surface:

attaches epithelial cells to underlying tissues


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• Basement Membrane

– Specialized type of extracellular material

– Secreted by epithelial and connective tissue cells

– Functions

• Attaches cells to underlying tissue

• Supports and guides cell migration


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Functions of Epithelial Tissues

1. Protect:

Ex. Skin

2. Act as a barrier:

Ex. Skin keeps bacteria out

3. Diffusion and Filtration:

Ex. Lungs and kidneys

4. Secretion:

Ex. Sweat glands

5. Absorption:

Ex. Small intestine


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Classification of Epithelial Tissue

• Classified according to number of cell layers

and cell shape

• Simple and stratified = number of cell layers

• Squamous, cuboidal, columnar, transitional= cell

shape


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Types of Epithelial Tissues

• Simple Epithelium

Structure: 1 layer of cells

• Stratified Epithelium

Structure: many layers of cells


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• Simple Squamous

Structure: 1 layer of flat, tile-like cells

Function: diffusion and filtration

Location: blood vessels, lungs, heart, kidneys

• Simple Cuboidal

Structure: 1 layer of square-shaped cells

Function: secretion

Location: glands, ovaries, kidneys


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• Simple Columnar

Structure: 1 layer of tall, narrow cells

Function: secrete mucus and absorption

Location: stomach, intestines, resp. tract

• Pseudostratified Columnar

Structure: 1 layer of tall, narrow cells

appears stratified but isn’t

Function: secrete mucus and propel debris out of

resp. tract (cilia)

Location: nasal cavity and trachea


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• Stratified Squamous

Structure: many layers of flat, tile-like cells

Function: protect and acts as a barrier

Location: skin, mouth, throat, esophagus

• Transitional

Structure: special type of stratified epi. changes

shape (stretched squamous, not stretched

cuboidal)

Function: hold fluids

Location: urinary bladder


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Tab.

4.2b


Tab

.

4.2c


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Free Cell Surfaces

• Surface not in contact with other cells

• Smooth to reduce friction, Ex. Blood vessels

• Microvilli:

- increase cell’s surface area

- Ex. Small intestine


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• Cilia:

- move materials across cell’s surface

- Ex. Trachea

• Goblet cells:

- produce mucus

- Ex. Stomach


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Cell Connections

• Tight junctions:

- bind adjacent cells together; permeability

barrier

- Ex. Intestines

• Desmosomes:

- mechanical links that bind cells

- disk-shaped

- adhesive glycoproteins & intermediate filaments


• Hemidesmosomes:

bind cells to basement membrane

• Gap junctions:

- small channels that allow molecules to pass

between cells

- allow cells to communicate

- most common

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Figure 4.2


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Glands • What are they?

structures that secrete substances onto a surface, into

a cavity, or into blood

• Exocrine glands:

- glands with ducts

- Ex. Sweat or oil glands

• Endocrine glands:

– no ducts (directly into bloodstream)

– Ex. Thyroid, thymus, pituitary glands, etc.


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Types of Exocrine Glands

• Simple:

no branches

• Compound:

many branches

• Tubular:

end of duct

• Alveolus:

sac-like structure

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Connective Tissues Characteristics

• Cells far apart

• Contain large amounts of extracellular matrix

• Classified based on type of extracellular matrix

and function

• Ex. Blast cells build, clast cells carve

• Extracellular matrix contains 3 components (in

varying amounts): protein fibers, ground

substance, fluid

• Ground substance: proteins and sugars


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Types of Protein Fibers

• Collagen fibers:

look like ropes and are flexible but resist

stretching

• Reticular fibers:

supporting network that fills spaces between

organs and tissues

• Elastic fibers:

recoil after being stretched


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Functions of Connective Tissue

1. Enclose and separate:

Ex. around organs and muscles

2. Connect tissues:

Ex. Tendons: connect bone to muscle

Ex. Ligaments: connect bone to bone

3. Support and Movement:

Ex. bones


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4. Storage:

Ex. bones store calcium and adipose tissue

stores fat

5. Cushion and insulate:

Ex. adipose tissue protects organs and helps

conserve heat

6. Transport:

Ex. Blood

7. Protect:

Ex. Immune cells


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Types of Ordinary Connective Tissue

• Loose

Location: between organs, muscles, glands, skin

Structure: collagen fibers far apart

Function: support and protect


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• Dense

Location: tendons, ligaments, skin

Structure: collagen fibers packed close together

Function: connect and can withstand pulling

forces

• Adipose

Location: under skin and around organs

Structure: collagen and elastic fibers, cells filled

with lipids

Function: storage, insulate, cushion


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Cartilage

• Type of connective tissue

• Composed of chondrocytes

• Contains collagen

• Withstands compressions

• Provides support, flexibility, strength

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Types of Cartilage

• Hyaline cartilage

Location: covers ends of bones

Structure: some collagen fibers

Function: reduces friction (cushion)

• Fibrocartilage

Location: between vertebra

Structure: lots of collagen fibers

Function: can withstand compression


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• Elastic cartilage

Location: ear and tip of nose

Structure: elastic fibers

Function: can recoil


Bone

• Hard connective tissue

• 2 types: compact and spongy

• Composed of osteocytes

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Blood

• Liquid connective tissue

• Erythrocytes,

leukocytes, platelets

• Transport food, oxygen,

waste, hormones

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Muscular Tissue Muscle type Nucleus/i Nucleus/i location Striated

Skeletal many peripheral Y

(most muscle)

Cardiac 1 centrally Y

(heart)

Smooth 1 centrally N

(organs)


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Nervous Tissue

• Consist of neurons or nerve cells

• Found in brain, spinal cord, and peripheral nerves

• Controls and coordinates body movements

• Includes axons, dendrites, cell bodies


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