Histology

TISSUES

Janice V. Ng, MSc

Department of Biology

CAS, UP Manila

Tissues

“weave”

group of cells with a common structure

and function

held together by intracellular substances

Types

Epithelial Tissues

Connective Tissues

Muscular Tissues

Nervous Tissues

Epithelial Tissues

composed of closely packed cells with very little intercellular substance

surface epithelia – exposed to air or fluid; continuous with one or more layer of cells

base of epithelia usually resting on a basement membrane

◦ Basement membrane – separates epithelia from underlying tissues; never penetrated by blood vessels

cover the outside of the body and line organs and cavities within the body

wide range of activities:

◦ protective covering and lining surfaces (skin), absorption (intestine), secretion (epithelial cells of glands), sensory (neuroepithelium) and contractility (myoepithelial cells).

Cell joined together by cellular junctions

Epithelial Tissues

Shape

squamous cuboidal columnar

Number

simple stratified

Stratified squamous

Pseudostratified

columnar

Name: Number of layers + shape

Example…

Simple epithelium

◦ ___ layer of cell

◦ Involved in selective diffusion, absorption,

secretion

◦ Protection?

Only minimal

Simple Squamous

Epithelium

• air sacs of lungs, glomeruli,

linings of heart, lymphatic and

blood vessels

• diffusion and filtration

Simple Cuboidal

Epithelium

• kidney tubules, ducts and

small glands and surface of

ovary

• secretion and absorption

Simple Columnar

Epithelium

• linings of digestive tract, gall

bladder, and excretory ducts

of some glands

• villi, microvilli, goblet cells

• absorption and enzyme

secretion

Stratified epithelium

◦ ____ layer of cells

◦ Mainly for protection

◦ Degree of stratification related to the kind of

physical stresses to which the surface is

exposed

◦ Name is based on the structure of the ____

cells

Stratified Squamous

Epithelium

• keratinized: surface of the

skin

• nonkeratinized:

linings of the esophagus,

mouth and vagina

• protect underlying tissues in

areas subject to abrasion

Pseudostratified

Ciliated Columnar

Epithelium•True simple epithelium

• All cells rest at the basement

membrane

• Nuclei disposed at different

levels

• Cilia

• Linings of bronchi, uterine

tubes, and some regions of the

uterus.

• propel mucus or reproductive

cells by ciliary action.

Connective Tissues

Provide structural and metabolic support

for other tissues and organs

Usually contain blood vessels

Mediate exchange of nutrients,

metabolites, waste products between

tissues and circulatory system

Connective Tissues

Basic Components

◦ Cells – scattered through extracellular matrix

Fibroblast/fibrocyte, Adipocytes, Mast cells, macrophages, Blood cells

◦ Extracellular Matrix

Fibers

Collagen, Elastin, Reticulin (Type III collagen)

Ground Substance - mixture of polysaccharide chains, glycosaminoglycans (GAGs), proteoglycans

Structural glycoproteins – mediates interaction of cells with other constituents

Connective Tissue

Connective Tissue Proper

Loose/Areolar

Dense Modified Loose

Specialized Connective

Cartilage

BoneBlood

Connective Tissue Proper - jelly-like extracellular matrix

Specialized Connective Tissue - liquid/ semi-solid/ hard solid matrix

Loose/ Areolar

Connective Tissue

• with numerous fibroblast

that produce collagenous and

elastic fibers

• subcutaneous layer

• wrap and cushions organs

Dense Regular Connective

Tissue

• contains densely packed

parallel collagen fibers

• tendon, ligaments

Dense Irregular

Connective Tissue

• contains densely packed

randomly arranged collagen

fibers

• Frog skin

Modified Loose Connective Tissue

Adipose Tissue

• subcutaneous layer

• cushions, storage of fats

Reticular Tissue

• supports hemopoietic organs

Cartilage Cell component – chondrocytes

Ground substance – chondroitin sulfate and hyaluronate

Fibers: collagen, elastic

Hyaline Cartilage

• collagen fibers

• cartilage of nose, trachea, larynx

• support and reinforcement

Elastic Cartilage

• collagen fibers and many elastic

fibers

• cartilage of external ear and

epiglottis

• maintains shape and allows

flexibility

Fibrocartilage

• dense collagen fibers

• cartilage of intervertebral disc,

pubic symphysis and disk of knee

joints

• absorbs compression shock

Bone

Cell Components – osteoblasts,

osteocytes, osteoclasts

Ground Substance – calcium

phosphate, chondroitin-sulfate

and keratan sulfate (hard and

mineralized matrix)

Fibers: collagen (Type I)

Blood

Granulocytes Agranulocytes

Neutrophil Eosinophil

Basophil

Lymphocyte

Monocyte

Erythrocytes Leukocytes

Muscle Tissue

Striated Voluntary Muscle (Skeletal

Muscle)

Striated Involuntary

Muscle (Cardiac Muscle)

Non-striated Involuntary Muscle (Smooth/Visceral

Muscle)

*Striations – arrangement of the contractile proteins (actin and myosin)

Skeletal Muscle Tissue

• striated muscle fibers

• cylindrical

• many peripheral nuclei

• skeletal muscles attached to

bones

• useful for voluntary

movement

• sarcolemma

• sarcoplasm

Cardiac Muscle Tissue

• striated muscle fibers

• branched, with intercalated

disc

• uninucleated

• involuntary heart movement

Smooth Muscle Tissue

• Spindle-shaped cells

• uninucleated

• lacks striations

• involuntary movement of

visceral organs and blood

vessels

• epimysium, perimysium,

endomysium

Nervous Tissues

Sense stimuli and transmit signals from one

part of the animal to another

Functional unit neuron/nerve cell

Smear, Cross section, Longitudinal section

Nervous Tissue (smear)

• cell body

• nucleus

• dendrites and axon

• glial cells

Axons are bundled together in structures

called nerves.

Longitudinal section

• Neurilemma- membrane covering the fiber

• Axis cylinder- the central region of the nerve

fiber

• Medullary sheath - thick sheath covering the

fiber between the neurilemma and the axis

cylinder

• Nodes of Ranvier- constrictions in the

medullary sheath

Cross section (not available)

• Epineurium - the membrane covering a

bundle of fascicule of nerve fiber

• Perineurium - the membrane covering a

fasciculus of nerve fiber

• Endoneurium - the membrane covering a

nerve fiber

END