Histology

Body Tissues

Cells are specialized for particular functions

Tissues

Groups of cells with similar structure and function

Extracellular Matrix

“cell glue” between cells

Histology

study of tissue

Body Tissues

Four primary types (functional categories)

Epithelium

protection /secretion /absorption/ filtration

Connective

support & structure

Nervous

communication & control

Muscle

movement (internal & external)

Primary Germ Layers

Endoderm

(Epithelial)

Mesoderm

(Epithelial, Muscle, Connective)

Ectoderm

(Epithelial, Nervous)

Digestive & respiratory

epithelium

Muscles Epidermis

Urethra epithelium Skeleton (bones & cartilage) Lining of mouth, anus,

nostrils

Bladder Blood Sweat & sebaceous

glands

Liver & pancreas Blood vessel epithelium Hair

Dermis Brain & spinal cord

Excretory & reproductive organs Eyes, nose, ear

epithelium

EPITHELIAL TISSUES

Epithelial Functions

Protection

Sensory

Secretion

Absorption

Excretion

Epithelium Characteristics High cellularity

cells fit closely together

very little EC matrix

Contains specialized contacts

tight junctions & desmosomes

Avascular

no blood vessels within it

diffusion provides nutrients & carries waste away

lots of nerve fibers

Reinforcement & connection

Defines boundaries

cancer causes a breach in these boundaries

Regenerate easily if well nourished

Found in areas of high friction

Classification of

Epithelium

Combination of shape & # of cells is used to name tissues

Shape of cells

Squamous – flattened

Cuboidal – cube-shaped

Columnar – column-like

Classification of Epithelium

Number of cell layers

Simple

one layer

found in areas of transport

Stratified

more than one layer

High abrasion areas for protection

Secretory membranes

Classification of Epithelium

• Pseudostratified • “False” layers

• Ciliated (respiratory tract)

• Non-ciliated (male urethra)

• Transitional • multiple layers of epithelial

cells, “hodge-podge”

• Found in urinary tract

• can look cuboidal until

bladder stretches, then

looks squamos

Keratinized Epithelium

Keratin

tough waterproof material

found in upper layers of some stratified squamos

epithelium

Non-Keratinized Epithelium

Epithelial Membranes

Mucous membranes

Line body cavities OPEN to the exterior

Example: digestive, respiratory, urogenital

Mucus protects by trapping microorganisms, substances in

mucus will destroy them

Cutaneous Membranes

Skin

Helps waterproof & protect body

First line of defense in immune system

Serous Membranes

Lines all CLOSED body cavities

Serous fluid located between layers to reduce friction due

to organ motion

Epithelial Membranes

Glandular Epithelium Gland

one or more cells that secretes a particular product

Two major gland types

Endocrine gland

Ductless – secretes product directly into blood or tissue

Produces hormones

Exocrine gland

Empty through ducts to the epithelial surface

Include sweat and oil glands

Glandular Epithelium • Apocrine

• secrete their product from intact cells

• Ex: Mammary glands

• Holocrine

• entire cells and their secretions accumulate as

the gland’s secretory product

• cells rupture

• Ex: Sebaceous (oil) glands

• Merocrine

• Most common

• accumulate their secretory product at the

apical surface of each cell, which then

separates from the remainder to form a

secretion in the lumen of the gland.

• cells then repair themselves.

• Ex: Salivary glands

Glandular Epithelium

Connective Tissue

Support & strengthen & provide structure

Connective Tissue Found everywhere in the body

Includes the most abundant and widely distributed tissues

Functions

Binds body tissues together

Supports the body

Provides protection

Insulates to maintain body temperature

Transportation of other molecules

Origin of Connective Tissue

Mesenchyme: embryonic tissue that

differentiates into all forms of CT

Connective Tissue

Characteristics

Variations in blood supply

Some tissue types are well vascularized

Adipose – danger of hemorrhage with liposuction

Some have poor blood supply or are avascular

Blood supply is necessary for healing

brings oxygen & “spare parts”

Extracellular Matrix Two main elements

Ground substance

proteins and polysaccharide molecules

function as a molecular sieve to diffuse nutrients & other substances

Fibers

Produced by the cells

Three types

Collagen fibers – tensile strength

Elastic fibers – stretch with recoil

Reticular fibers - support

Connective Tissue Cells

Prefixes

Fibro

Osteo

Chondro

Hemo(cyto)

Suffixes

Blast – build the cells

Cyte – cell

Clast – breakdown the cells

Connective Membranes

Synovial

Lines spaces between bone and joint

Secrete synovial fluid to reduce friction

Connective Tissue Outline

Bone

Cartilage

Hyaline

Fibrocartilage

Elastic

Perichondrium

Fibrous

Areolar (Loose connective)

Adipose

Reticular

Dense fibrous

Regular

Irregular Blood

Plasma

Cells

Eryhtrocytes

Leukocytes

Thrombocytes

Connective Tissue Types - BONE

Bone (osseous tissue)

Composed of:

Bone cells in lacunae (cavities)

Hard matrix of calcium salts

Large numbers of collagen fibers

Osteon – primary anatomical and functional unit of compact bone

Used to protect and support the body

Hematopoiesis – formation of blood cells

Connective Tissue Types - CARTILAGE

Hyaline cartilage

Most common cartilage

Composed of:

Abundant collagen fibers

Rubbery matrix

Avascular

Found in

Entire fetal skeleton

Ventral ends of ribs

Articular surface of bones

Fibrocartilage

Highly compressible

Strongest & most durable

forms cushion-like discs between vertebrae, pubic symphysis, meniscus

Connective Tissue Types - CARTILAGE

Elastic cartilage

Provides elasticity, very flexible

Supports the external ear, larynx

Connective Tissue Types - CARTILAGE

Perichondrium

Surrounds cartilage

Connective Tissue Types - CARTILAGE

Connective Tissue Types - FIBROUS

Areolar (Loose Connective)

Most widely distributed connective tissue (surrounds blood vessels & nerves)

Soft, pliable tissue

Contains all fiber types

Can soak up excess fluid

Main function – to cushion and protect organs

Types of fibers

Collagenous - collagen

Elastic – elastin , stretchable

Reticular – very thin

Connective Tissue Types - FIBROUS

Adipose

Matrix is an areolar tissue in which fat globules predominate

Many cells contain large lipid deposits

Functions

Insulates the body

Protects some organs

Serves as a site of fuel storage

Adipose

Connective Tissue Types - FIBROUS

Reticular

Delicate network of interwoven fibers

Holds together adipose tissue

Forms stroma (internal supporting network) of lymphoid organs; soft skeleton

Lymph nodes

Spleen

Bone marrow

Connective Tissue Types - FIBROUS

Dense fibrous

Main matrix element is collagen

fibers

Cells are fibroblasts

Irregular – not parallel

dermis

Regular - parallel

Tendons – attach muscle to bone

Ligaments – attach bone to bone

Connective Tissue Types - FIBROUS

Regular

Irregular

Connective Tissue Types - FIBROUS

Connective Tissue Types - BLOOD

Fibers are visible during clotting

Functions as the transport vehicle for materials

55% Liquid component

plasma

45% Blood cells

Erythrocytes - RBC

Leukocytes - WBC

Thrombocytes - platelets

Connective Tissue Outline

Bone

Cartilage

Hyaline

Fibrocartilage

Elastic

Perichondrium

Fibrous

Areolar (Loose connective)

Adipose

Reticular

Dense fibrous

Regular

Irregular Blood

Plasma

Cells

Eryhtrocytes

Leukocytes

Thrombocytes

Muscle Tissue

Highly vascular & highly cellular

Less matrix = more flexibility

More blood flow = more ATP made

Actin & myosin – contractile myofilaments

Function is to produce movement

3 types

Skeletal

Smooth

Cardiac

Muscle Tissue Types Skeletal muscle

Can be controlled voluntarily

Cells attach to connective tissue

Cells are striated

Cells have more than one nucleus

attached to bone

Smooth muscle

Involuntary muscle

Surrounds hollow organs

Attached to other smooth muscle cells

No visible striations

One nucleus per cell

Viscera of hollow internal organs

Cardiac muscle

Found only in the heart

Function is to pump blood (involuntary)

Cells attached to other cardiac muscle cells at intercalated disks

Cells are striated

One nucleus per cell

Muscle Tissue Types

Nervous Tissue

Consists of brain, spinal cord, nerves

Carry electrical signals

Neurons: generate & conduct electricity

Usually nonregenerative

Neuroglia: support neurons

Tissue Repair

Determination of type of repair

Type of tissue damaged

Severity of the injury

Regeneration

Replacement of destroyed tissue by the same kind of cells

Fibrosis

Repair by dense fibrous connective tissue (scar tissue)

Regeneration of Tissues

Regenerate easily

Epithelial tissue

Bone

Regenerate poorly

Skeletal muscle – replaced with connective tissue, not muscle

Cartilage

Nervous

Replaced largely with scar tissue

Cardiac muscle

Nervous tissue within the brain and spinal cord

Connective - keloids

Steps of Tissue Repair

1. capillaries dilate – brings blood to supply clotting

factors

2. clot forms – seal off injury

3. scab forms – protect injury

4. debris is cleaned out – macrophages eat away

damaged tissue to leave room for repair

5. Organization of tissue parts – granulation occurs (a

type of intermediate tissue)

6. Macrophages digest & remove original clot

7. Surface epithelium regenerates – scab usually falls

off at this time

End result: Healed injury!

Tissue Disease