The Tissue Level of Organization

Introduction

Histology: the study of tissues– Tissue: composed of cells, and extracellular

materials & fluids 4 Types of Tissues:

– A) Epithelial: covers surfaces, lines passageways & chambers, produces gland secretions

– B) Connective: fills internal spaces, supports & binds organs, stores energy

– C) Muscle: contracts to produce movement– D) Neural: conducts electrical impulses & carries

info throughout body

Epithelial Tissue

Includes epithelia & glands Functions:

– 1) Provides protection– 2) Controls skin permeability– 3) Provides sensation– 4) Produces gland secretions

Epithelial Cells (con’t)

Shapes: – Squamous– Cuboidal– Columnar

Arrangements:– Simple: single layer– Stratified: multiple layers– Pseudostratified: single layer, but appears to be

multi-layered• All cells attach to basement membrane

Epithelial Tissue - Simple

Simple Squamous: lines ventral body cavities & blood vessels– decreases friction, provides absorption & secretion

Simple Cuboidal: glands & ducts– protection, absorption, secretion

Simple Columnar: lines stomach, intestines, gallbladder, uterine– protection, absorption, secretion

Epithelial Tissue - Other

Pseudostratified Ciliated Columnar: lines nasal cavities, trachea & bronchi– protection & secretion

Transitional: urinary bladder, ureters– allows expansion & recoil for stretching

Stratified Squamous: skin surface, lines mouth, throat, esophagus– protects against abrasion, pathogens & chemicals

Connective Tissue

Includes: bone, cartilage, blood, fat, etc. Composed of:

– specialized cells surrounded by a matrix (protein fibers & ground substance fluid)

Functions:– 1) Support & Protection– 2) Transport of Materials– 3) Energy Storage– 4) Body Defenses

Types of Connective Tissue

Connective Tissue Proper Types

1) Loose “areolar”– Separates skin from muscle, provides padding, &

contains extensive blood supply

2) Adipose (loose with many fat cells)– Provides shock absorption, insulation, energy

storage

3) Dense “fibrous/collagenous”– Tendons: connect muscle to bone– Ligaments: connect bone to bone

Supporting Connective Tissue

Cartilage: composed of chondrocyte cells & covered in perichondrium; NO blood supply– Hyaline cartilage: connects ribs to sternum &

covers joints– Elastic Cartilage: forms outer ear & epiglottis– Fibrocartilage: pad between vertebrae & in pubic

bone

Bone: composed of osteocyte cells & covered in periosteum; EXTENSIVE blood supply

“Membranes”

May refer to plasma membrane, a barrier (i.e. basement membrane), OR

A covering composed of epithelia tissue & connective tissue

Types of Membranes 1) Mucous: line cavities that communicate

with the exterior (i.e. respiratory, reproductive, & urinary tracts)– Kept moist by secretions & fluids

2) Serous: line sealed, internal divisions of body cavities (i.e. heart, lungs, etc.)– ↓ friction & allows for movement

3) Cutaneous: covers the body (skin)– Provides thick, waterproof protection

4) Synovial: fills cavities in bone joints– Lubricates and ↓ friction in joints

Muscle Tissue

Contraction involves the action of myosin & actin proteins

3 Types:– 1) Skeletal: composed of large,

multinucleated cells• Most large muscles in the body• Appear striped, or STRIATED• Under VOLUNTARY control of

nervous system

Muscle Tissue (con’t) Types:

– 2) Cardiac: striated, but composed of small, single-nucleus cells

• Compose most of the heart• Controlled by pacemaker cells in

heart (not nervous system)• Under INVOLUNTARY control

– 3) Smooth: non-striated & composed of long, slender single-nucleus cells

• Line blood vessels, urinary bladder, resp. & digest. tracts

• Under INVOLUNTARY control of nervous system

Neural Tissue Conducts electrical impulses throughout

the body Mostly found in brain and spinal cord Composed of 2 types of cells:

– 1) Neurons: send & receive impulses– 2) Neuroglia: provide support, nutrition, &

defense for neurons

Tissue Injury and Repair

After injury happens, 2 processes occur:– 1) Inflammation: includes swelling, warmth,

redness, & pain• Mast cells release chemicals to ↑ blood flow & stimulate

nerve endings at injured area

– 2) Regeneration: fibroblasts produce scar tissue• Skin, most connective tissues, & smooth muscles

regenerate well• Striated muscles & nerve cells do not• Fibrosis: replacement of cardiac tissue with fibrous

connective tissue