Histology

The study of cells and tissues

Histology – Objectives

what are the diagnostic characteristics of each of the four main types of tissues

what are the diagnostic characteristics of each of the subtypes of tissues

be able to give examples of each tissue type

are organs made of one or more tissues?

Tissues – 4 basic types epithelial connective muscular nervous

Tissues – 4 basic types

epithelium – forms internal or external linings of organs and

glands, specialized for lubrication, resisting abrasion, water-

proofing, absorption, and/or secretion; rests on basement

membrane; basal to apical or luminal polarity; one free surface;

cellularity; specialized cell junctions including desmosomes or tight

junctions; rapid regeneration; nourishment by diffusion; no intrinsic

vascularization or innervation

connective –

muscular –

nervous –

Epithelium (pl. epithelia)

simple squamous stratified squamous

simple cuboidal stratified cuboidal

simple columnar pseudostratified columnar

transitional

glands – (made of epithelium, but not a type thereof)

Epithelium (pl. epithelia)

simple squamous stratified squamous

flat, single layered multilayered with basal germinal layer

endothelium of blood vessels epidermis of skin

simple cuboidal stratified cuboidal

glands and their ducts gall bladder, sexual ducts

simple columnar pseudostratified columnar

cells tall, parallel cells tall, not parallel

brush border or microvilli ciliated

endothelium of intestines endothelium of trachea

transitional

urinary bladder

glands – both excretory and secretory

endocrine – ductless

exocrine – possess ducts

shape: tubular, alveolar, simple, complex

simple squamous stratified squamous flat, single layered multilayered with basal germinal layer e.g., endothelium of blood vessels e.g., epidermis of skin

simple cuboidal stratified cuboidal e.g., glands and their ducts e.g., glands and their ducts gall bladder, sexual ducts

simple columnar pseudostratified columnar cells tall, parallel cells tall, not parallel brush border or microvilli ciliated e.g., endothelium of intestines e.g., endothelium of trachea

transitional urinary bladder

glands – both excretory and secretory endocrine – ductless exocrine – possess ducts shape: tubular, alveolar, simple, complex

Tissues – 4 basic types

epithelium –

connective – acellularity; extracellular matrix>>cells; provides

structure and/or substrate for blood vessels, nerves, lymphatics,

and glands; extracellular matrix or ground substance = water,

dissolved or precipitated salts, proteins, and carbohydrates

muscular –

nervous –

Connective Tissues Non-binding Connective Tissue blood/lymph

Binding Connective Tissue loose connective tissue dense connective tissue cartilage bone

Non-binding Connective Tissue blood/lymph – formed elements = cellular, plasma = water, dissolved

salts, nutrients, nitrogenous waste, CO2, albumin, fibrinogen, globulins

Binding Connective Tissue loose connective tissue – little protein in extracellular matrix

areolar – collagen, forms interstitia

adipose – lipid droplets, fat

reticular – reticulin, net or filter structure of lymph organs

dense connective tissue – much protein in extracellular matrix

regular – parallel collagen fibers, e.g., tendons

irregular – nonparallel collagen fibers, e.g., dermis of skin

elastic – elastin, rebounds after deformation, e.g., arteries

cartilage – extracellular matrix with glycosaminoglycans, chondroitin

sulfate, hyaluronic acid; chondrocytes reside in lacunae; interstitial and

appositional growth

hyaline – collagen, most common type in skeletal system

elastic – elastin, e.g., pinna of ear, epiglottis

fibrous – fibrin, very tough joints, e.g., intervertebral discs

bone – highly vascularized extracellular matrix of precipitated collagen

and apatite [Ca3(PO4)2]; osteocytes reside in lacunae; appositional

growth only

Non-binding Connective Tissue blood/lymph

Loose Connective Tissue – little protein in extracellular matrix areolar – collagen, forms interstitia adipose – lipid droplets, fat

reticular – reticulin, net or filter structure of lymph organs (not shown)

Dense Connective Tissue – much protein in extracellular matrix regular – parallel collagen fibers irregular – nonparallel collagen fibers e.g., tendons e.g., dermis of skin

elastic – elastin, rebounds after deformation e.g., arteries

fibrous – fibrin, very tough joints e.g., intervertebral discs

Cartilage – extracellular matrix with glycosaminoglycans, chondroitin sulfate, hyaluronic acid; chondrocytes reside in lacunae; interstitial and appositional growth hyaline – collagen, most common type elastic – elastin, e.g., skeletal system e.g., pinna of ear, epiglottis

Bone – highly vascularized extracellular matrix of precipitated collagen and apatite [Ca3(PO4)2]; osteocytes reside in lacunae; appositional growth only

Tissues – 4 basic types

epithelium –

connective –

muscular – electrochemically excitatory and contractile

nervous –

Muscular Tissue – Ca++ and ATP dependent contraction; protein

myofilaments of two types: thin filaments – actin, troponin, meromyosin, others depending on muscle type; and thick filaments – myosin smooth muscle striated muscle skeletal striated muscle cardiac striated muscle

Muscular Tissue – Ca++ and ATP dependent contraction; thin filaments –

actin, troponin, meromyosin; thick filaments – myosin

smooth muscle – spindle shaped cells, mononucleate, in walls of organs (e.g.,

digestive tract, blood vessels, skin), respond to hormones, stretch, and

innervation by autonomic nervous system

striated muscle – myofilaments bundled into myofibrils forming ‘striated’

sarcomeres (alternating interdigitating bands of thick and thin filaments),

juxtaposed to sarcoplasmic reticulum (ER sequesters Ca++) and transverse

tubules (invaginations of sarcolemma); numerous mitochondria

skeletal striated muscle – giant multinucleate linear cells of voluntary skeletal

muscular system, syncytium, every cell innervated with motor endplate,

responds to neurotransmitter acetylcholine; denervation results in atrophy

cardiac striated muscle – myocardium of heart; branching cells joined at

intercalated discs; syncytium but few nuclei; intercalated discs possess gap

junctions (electrical connectivity) and desmosomes; cells depolarize

spontaneously and wave of contraction passes from cell to cell; rate modulated

by hormones and autonomic innervation

Smooth Muscle – fusiform shaped cells, mononucleate, in walls of organs (e.g., digestive tract, blood vessels, skin), respond to hormones, stretch, and innervation by autonomic nervous system

Striated Muscle – myofilaments bundled into myofibrils forming ‘striated’ sarcomeres (alternating interdigitating bands of thick and thin filaments), juxtaposed to sarcoplasmic reticulum (ER sequesters Ca++) and transverse tubules (invaginations of sarcolemma); numerous mitochondria

Skeletal Striated Muscle – giant multinucleate linear cells of voluntary skeletal muscular system, syncytium, every cell innervated with motor endplate, responds to neurotransmitter acetylcholine; denervation results in atrophy

Cardiac Striated Muscle – myocardium of heart; branching cells joined at intercalated discs; syncytium but few nuclei; intercalated discs possess gap junctions (electrical connectivity) and desmosomes; cells depolarize spontaneously and wave of contraction passes from cell to cell; rate modulated by hormones and autonomic innervation

Tissues – 4 basic types

epithelium –

connective –

muscular –

nervous - electrochemically excitatory and conductive

Nervous Tissue

neuroglia or glial cells neurons

Nervous Tissue

neuroglia or glial cells – structural, supportive, insulating

neurons – excitatory; cell body or ‘neuron’; cell processes

are axons and dendrites; slow transport of neurotransmitters

from neuron to presynaptic vesicles of axon; membrane

depolarization causes release of neurotransmitters into

synapse which are bound by receptors of postsynaptic

dendrites; neurotransmitters may be excitatory, inhibitory, or

modifying to membrane depolarization of postsynaptic

neuron

Neurons – excitatory; cell body or ‘neuron’; cell processes are axons and dendrites; slow transport of neurotransmitters from neuron to presynaptic vesicles of axon; membrane depolarization causes release of neurotransmitters into synapse which are bound by receptors of postsynaptic dendrites; neurotransmitters may be excitatory, inhibitory, or modifying to membrane depolarization of postsynaptic neuron

Neuroglia or glial cells