Chapter 5: Histology

Histology definition

Study of Tissue

(Histology (microscopic anatomy)

- study of tissues and how they form organs)

How many cell types in body?

200 cells types in body's

4 Basic Tissues

Epithelial: (Free surface)

Connective: (Matrix)

Muscle: (Contracts)

Nervous

Tissue Define

an aggregation of similarly specialized cells which together perform certain specific functions

Organ Define

complex and consists of at least 2 tissue types

Epithelial Tissue: General Features

- good at either protection or support not both

- occur in sheets and layers

- avascular

- highly cellular (not a lot of matrix)

- directional (apical vs basal)

- divides tissue from outside world

4 shapes of epithelial cells

Classified by shape of surface cells

- squamous (flat)

- cuboidal (cube shaped)

- columnar (tall column)

- transitional (shape varies with tissue stretching)

Arrangement of Epithelial Tissue

- simple (one cell thick)

- pseudostratified (single layer of cells where all cells don't reach apical surface)

- stratified (many layers thick)

Basement Membrane

Basal lamina:

- from epithelial cells

- collagen fibers

Reticular lamina

- secreted by connective tissues

- reticular fibers

Holds cells to connective tissues

Guide for cell migration during development

5 systems that have epithelial tissue

Integument (external skin)

Digestive (digestive tract)

Pulmonary (lungs)

Urinary (urethra to kidney)

Reproductive (uterus/vagina)

Simple Squamous Epithelium

- Single layer of thin cells

- permits rapid diffusion of substances

- poor protection

Simple Cuboidal Epithelium

- single layer of square or round cells

- active transport (absorption or secretion) requires space for organelles inside cell

- limited protectoin

Nonkeratinized Stratified Squamous Epithelia

internal mucousa that are protective but lack keratin

- tongue, oral mucosa, esophagus, vagina

- resists abrasion and penetration of pathogens

Keratinized Stratified Squamous Epithelia

- found on skin surface

- keratin increases abrasion resistance

- multiple cell layers (cells flatter at surface)

- external epidermis

- excellent protection

Stratified Squamous Epithelia

- deepest layers undergo continuous mitosis (daughter cells push toward surface and become flatter as they migrate)

- 2 kinds:

keratinized

non-keratinized

Stratified Cuboidal Epithelia

- 2 or more cell layers

- surface cells square or round

- uncommon

- seen in glands

Transitional Epithelium

- multilayered

- sufrace cells change from round to flat when stretched

- urinary tract only (bladder)

2 Parts of Extracellular Material

1. fibrous proteins

2. ground substance

Pseudostratified Epithelium

- Looks multilayered (all cells touch basal layer)

- nuclei at several layers

- often ciliated (lungs)

Connective Tissue Functional Diversity

- bind organs

- support/physical protection

- immune protection

- movement

- storage

- transport

Cells of Connective Tissue

Fibroblasts

Macrophages

Neutrophils

Mast cells

Plasma

Adipocytes

Osteyocyte (bone)

Chondrocyte (cartilage)

Areolar Tissues (no defining structure)

Fibers of Connective Tissue

Collagen

Elastic

Reticular

Ground Substance

Fluid to gelatinous

Fluid: interstitial or plasma

Solid/crystalline: bone

often intermediate and gelatinous: due to proteoglycans that associate with water

Proteoglycan Molecule

carbohydrate binds to water

Types of Fibrous Connective Tissue

Loose connective tissue

- gel like ground substance between cells

3 types

- areolar

- reticular

- adipose

Dense connective tissue

- fibers fill the spaces between cells

2 types (varying fiber orientation)

- dense regular connective tissue

- dense irregular connective tissue

Areolar Connective Tissue

underlines all epithelia and packages organs

All 3 fibers

- collagen

- reticular

- elastic

Gelatinous ground substance

Nuclei mostly fibroblasts

Reticular Tissue

Loose network of reticular fiber and cells

Forms supportive framework (stroma) for lymphatic organs

- lymph nodes

- spleen

Adipose Tissue

dominant cell type

energy storage, insulation, cushioning

subcutaneous fat and organ packaging

primarly cellular: little extracellular matrix

Dense Regular Connective Tissue

Densely packed parallel collagen fibers

Compressed fibroblast nuclei

withstands stress in one direction

very low cellular component (Lots of extracellular collagen)

Tendons & Ligaments

Dense Irregular Connective Tissue

densely packed, randomly arranged, collagen fibers

Withstand stress applied in multiple dimensions

Deeper layer of skin

Capsules around organs

Fibroblast mostly extracellular

Cartilage

Supportive CT with rubbery matrix

chondrocytes are unique cell type

Avascular

- diffusion brings nutrients and removes waste

- heals slowly

Major types (depend on fiber types)

-hyaline

- elastic

- fibrocartilage

Hyaline Cartilage

Most common type of cartilage

Clear glassy matrix because of unusual fineness of collagen fibers

Elastic Cartilage

only cartilage containing elastic fibers

flexible elastic support

external ear

epiglottis

Fibrocartilage

large, coarse bundles of parallel collagen fibers

resists compression and absorbs shock

found in symphyses (intervertebral and pubic) and menisci in knee

2 Forms of Osseous Tissue

Spongy Bone

Compact Bone

Osseous Tissue

low cellular proportion: primarily solid extracellular matrix

osteocytes are defining cell type

Blood

Fluid connective tissue

transports cells and dissolved matter from place to place

approx. 50% cellular & 50% acellular matrix

plasma is acellular matrix (lacks fibers unless coagulation occurs)

cellular portion: blood cells and cell fragments

3 Types of Muscle Tissue

- skeletal

- cardiac

- smooth (vasoconstriction)

4 characteristics of muscle tissue

1. excitable

2. specialized to contract in response to stimulation

3. exert physical force on bones, other tissues and organs

4. moves limbs, digestion, waste elimination, breathing, speech and blood circulation

Skeletal Muscle

Cells are long cylinders with many peripheral nuclei

Visible striations

Voluntary control

Cardiac Muscle

Cells are branched cylinders with one nuclei

Involuntary and striated

Attached by desmosomes

Communicate by intercalated discs

Smooth Muscle

Spindle shaped cells with a single central nuclei

Walls of hollow organs

- blood vessels

- GI tract

- bladder

Involuntary and non-striated

Cell Junctions

Tight junctions

Adherens junctions

Gap junctions

Desmosomes

Hemidesmosomes

Tight Junctions

Watertight seal between cells

Plasma membrane fused with strip of proteins

Common between cells that line GI and bladder

(like zipper)

Partial fusion of portions of the cell

Adherens Junctions

Hold epithelial cells together

Structural components

- plaque

dense layer of proteins inside cell membranes

- microfilaments

extend into cytoplasm

- integral membrane proteins

connect to membrane of other cell

(like velcro)

Desmosomes

Resists cellular separation and cell disruption

Similar structure to adherens except intracellular intermediate filaments cross cytoplasm of cell

Cellular support of cardiac muscle

(plaque like glue - can't break)

Hemidesmosomes

Half a desmosome

Connect cells to extracellular material

- basement membrane

Gap Junctions

Tiny space between plasma membranes of 2 cells

Crossed by protein channels called connexons forming fluid filled tunnels

Cell communication with ions and small molecules

Muscle and nerve impulses spread cell to cells

- heart and smooth muscle of gut

Endocrine and Exocrine Glands

Glands secrete substances for elimination or for use elsewhere in body

- composed primarily of epithelial tissue

Exocrine glands connect to surface

- epithelial tubes

Endocrine glands have no ducts

- secrete products (hormones) in bloodstream

Mixed organs

- liver

secretes bile into ducts, albumin into blood

- gonads

release gametes, secretes hormones into blood

- pancreas

secretes digestive enzymes and hormones

Types of Exocrine Glands

Simple glands have unbranched duct

Compound glands have a branched ducts

Shape of gland

- acinar (alveolar)

secretory cells form dilated sac instead of a tube

- tubuloacinar

secretory cells in both tubes and sacs

Methods of Glandular Secretion

Merocrine

- cells release products by exocytosis

- saliva, digestive enzymes, sweat

Apocrine

- upper parts of cell possibly pinches off and dies

- smelly sweat and milk

Holocrine

- whole cells die and rupture to release their products

- oil glands

Holocrine Gland

Secretory cells disintegrate in order to deliver their accumulated product and some cell fragments

Oil producing glands of scalp

Merocrine and Apocrine Secretion

Merocrine glands release their product by exocytosis

- tears, gastric glands, pancreas,

Apocrine glands are really merocrine glands but confusing appearance

- apical cytoplasm not lost as used to be believed

- mammary and armpit sweat glands

Mucous Membranes

Consists of

- epithelium

- lamina propria

- muscularis mucosae

Lines passageways that open to exterior

- digestive

- respiratory

- urinary

- reproductive

Mucous coating and movement of cilia trap and remove foreign particles/bacteria from internal surfaces

which primary tissue type does internal lining of intestine belong?

epithelial

what are the 4 primary tissues types

muscular, nervous, connective, epithelial

what primary tissue type do neuroglial cells belong to?

nervous

what primary tissue type does smooth muscle cells belong to?

muscular

what primary tissue type does adipose tissue belong to?

connective

what primary tissue type does cartilage belong to?

connective

what common cells are found in many diffrent types of connective tissue?

fibroblast (make elastic and reticular fibers and collagen)

Membrane excitability due to rapid changes in membrane potential is most pronounced in what two primary tissue types?

nervous and muscular

What two categorical components make up the extracellular matrix of connective tissue?

fibrous proteins and ground substance

When I rub my skin, am I touching the basolateral or apical side of that tissue?

apical (also where food touches)

What "specific" type of tissue (specific category and primary tissue type) underlies most epithelia?

primary: connective

specific: areolar

Name two categories of tissue where avascularity is a characteristic.

epithelial tissue and cartilage connective tissue are avascular

What type of connective tissue typically forms the strong capsule of organs?

dense irregular connective tissue

Characterize adipose tissue, blood, dense regular connective tissue, and stratified squamous epithelium in general as having a High, Moderate, or Low cellular contribution to the total volume.

adipose tissue = high

blood = moderate

dense regular connective tissue = low

stratified squamous epithelium = high

What specialized type of epithelium is specialized for transport by passive processes (diffusion)?

simple squamous epithelium

What type(s) are specialized for more active transport processes?

simple columnar epithelium and simple cuboidal

What specific type of epithelium is most highly specialized for protection and strength, but not absorption or secretion?

keratinized stratified squamous epithelium

3 Ways to Section Tissue

longitudinal section, cross section, oblique section

2 Types of microscopes

light microscope

scanning electron microscope (SEM) 3D visualization

4 steps for slide preparation

embedding (in paraffin or freeze)

sectioning (slicing)

fixing (dehydration/add alcohol)

staining

6 types of histological analysis

composition analysis

tissue culture

histopathology (tissues gone rogue)

marking/tagging

fluorescence

video

Nervous Tissue Specialization

specialized for communication by electrical and chemical signals

2 components make up nervous tissue

neurons (nerve cells)

- integration of stimuli

neuroglia (glial)

- protect and assist neurons

Nerve Tissue

Cell types

- neurons (nerve cell)

- glial cells

Nerve cell structure

- nucleus and long cell processes

- dendrite (signal towards cell body)

- axon (signal away from cell body)

2 places to find nervous tissue

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

excitability in nervous tissue

- a characteristic of all living cells

- developed to the highest degree in nervous and muscular tissue

membrane potential in nervous tissue

electrical charge difference (voltage) that occurs across the plasma membranes is the basis for the excitation

chemical communication in nervous tissue

occurs at synapses between neurons or between neurons and other effector tissues

effector = muscle or gland

2 excitable tissue types

nervous and muscle tissue

Integument Epithelial Tissue

excellent protection bad at transport

Pulmonary Alveoli Epithelial Tissue

excellent transport/diffusion bad at protection

Mesothelia Epithelial TIssue

Internal non free surface type

- lines organs (serous membranes)

- visceral vs. parietal layers

- heart (pericardium), lungs (pleura), viscera (peritoneum)

Glandular Epithelia and their shapes

sweat gland = exocrine gland

Simple Columnar Epithelium

-single row of tall, narrow cells & single row of nuclei

- active transport process (secretion and absorption)

- some protection

What are the three primary types of fibers found within the matrix of various connective tissues?

what macromolecule are they made of?

elastic fiber - in matrix (extracellular material)

reticular fiber - in matrix (extracellular material)

collagen - in matrix (extracellular material)

protein

What molecule differentiates outside skin of cheek from inside skin of mouth?

what macrololecules is it?

keratinized is outside skin, non-keratinized is inside skin

keratin is the protein/molecule that differentiates the two

protein

What specific tissue type is primarily associated with lymphatic organs such as the spleen?

reticular tissue

What two categories of cells are found within nervous tissue?

neurons and neuroglial cells

What unique type of epithelium is associated with the lining of much of the urinary system, such as the bladder?

is it stratified?

what special ability does it have?

transitional epithelial (only in urinary tract)

yes stratified

able to change from round to flat when stretched

3 types of cartilage

hyaline cartilage

elastic cartilage

fibrocartilage

What specific epithelial tissue appears stratified but in actuality is not stratified?

pseudostratified epithelia (looks multilayered but isnt)

What are the three subtypes of muscle tissue?

cardiac

smooth

skeletal

are hormones secreted from endocrine glands or exocrine glands?

endocrine glands

What type of epithelium lines internal/visceral organs (heart, lung, digestive)?

mesothelial: internal non free-surface type (simple squamous)

Are sweat glands exocrine or endocrine?

exocrine glands

By weight or volume, what is the most common general protein in the human body?

what color is it?

collagen

white