Histology

Ms. Levensailor

Animal Tissues

• Hierarchy: cells tissues organs organ systems• Tissues: groups of cells with a common structure

and function.– Held together by :

• Sticky substance • Woven together like a fabric

• From a Latin word meaning “weave”Note: Use the provided graphic organizer to take

notes.

4 Main Categories

• Epithelial tissue• Connective tissue• Muscles tissue• Nervous tissue

• With your face partner brainstorm the location and function of these tissue based on prior knowledge or their names.

Epithelial Tissue

• Cover the outside of the body and lines organs/cavities within the body.

• Closely joined/packed cells.• Functions as a barrier against injury, invading

organisms, fluid loss.– Structure matches function!

Epithelial Tissue

• Free surface is exposed to air or fluid.• Cells at the base of the barrier are attached to

the basement membrane (dense layer of extracellular material).

• Criteria for Classification:– Number of cell layers.– Shape of the cells on the free surface.

Number of cell layers

• Simple: single layer of cells.• Stratified: multiple tiers of cells.

Shape of Cells

• Cuboidal: like dice• Columnar: like long

bricks• Squamous: like flat floor

tiles

Put the words together. . .

Epithelial Tissue

Structure & Function

• Simple squamous: relatively leaky.– Used for exchange of materials (diffusion)– Linings of blood vessels and air sacs of the lungs.

• Stratified squamous: regenerates rapidly by cell division.– Used as replacements for cells that are continually

sloughed off. – Outer skin linings like the esophagus.

Structure & Function

• Columnar epithelia: large cytoplasmic volume.– Located where secretion or active absorption of

substances are important.– Stomach and intestines.

• Cuboidal cells: specialized for secretion. – Kidney tubules, thyroid gland, and salivary glands.

Check for Understanding

• Grab a whiteboard and marker.• What type of tissue is this?

Simple squamous

Check for Understanding

• What type of tissue is this?

Stratified squamous

Check for Understanding

• What type of tissue is this?

Simple cuboidal

Check for Understanding

• What type of tissue is this?

Stratified cuboidal

Check for Understanding

• What type of tissue is this?

Simple columnar

Connective Tissue

• Function: to bind and support other tissues.• Sparse population of cells scattered through

an extracellular matrix.– Matrix: nonliving, web of fibers embedded in a

homogeneous substance (liquid, jelly, or solid).– Secreted by the cells of the connective tissue.

Connective Tissue• Major types:

– Loose connective tissue*– Adipose tissue*– Fibrous connective tissue– Cartilage– Bone*– Blood

*These will be our focus.

Loose Connective Tissue

• Used as:– Binding to attach epithelia to underlying tissue.– Packing material to hold organs in place.

• Made of a loose weave of fibers.• 3 types of fibers:– Collagenous – Elastic– Reticular

Loose Connective Tissue

Adipose

• Specialized connective tissue: stores fat in cells throughout the matrix.

• Functions:– Pads and insulates the

body.– Stores fuel molecules.

• Cells contain large fat droplet that swells when fat is stored.

Bone

• Mineralized connective tissue.

• Cells called osteocytes: deposit a matrix of collagen & release calcium phosphate.– Combination makes

bone harder than cartilage without being brittle.

Check for Understanding

• What type of tissue is this?

Loose Connective Tissue

Check for Understanding

• What type of tissue is this?

Bone

Check for Understanding

• What type of tissue is this?

Adipose

Muscle Tissue

• Composed of long excitable cells.• Capable of contraction.• Large numbers of microfilaments run parallel

within cytoplasm of cells.– Made of actin and myosin (contractile proteins).

Types of Tissue

• Skeletal • Cardiac• Visceral (smooth)

Skeletal

• Responsible for voluntary movements of the body.– Adults have a fixed number of muscle cells.– Weight lifting does not increase cell number, just

enlarges cells.• Also called striated muscle : overlapping

microfilaments give the cells a striped appearance.

Cardiac

• Forms the contractile wall of the heart.– Striated, but branched.

• Causes rhythmic beating and contractions of the heart (uncontrollable).

Visceral (smooth)

• Lacks cross-striations.• Found in: Walls of the

digestive tract, bladder, and arteries.

• Involuntary: not subject to conscious control.

Muscle Tissue Review

Check for Understanding

• What type of tissue is this?

Smooth muscle

Check for Understanding

• What type of tissue is this?

Cardiac muscle

Check for Understanding

• What type of tissue is this?

Skeletal muscle

Nervous Tissue

• Senses stimuli and transmits signals.

• Functional unit is the neuron.– Consists of:

• a cell body• Nerve processes (two or

more appendages)– Dendrites: process

impulses toward the cell body

– Axons: transmit impulses away from the cell body

Nervous Tissue