Chapter 4: Histology

Histology

the study of tissues

collagen fiber

elastic fiber

Definition of tissues

the collections of specialized cells and the extracellular substance surrounding them

the purpose of a biopsy

for diagnostic purposes (Ex: to diagnose Celiac)

What is an autopsy?

examination of organs to determine cause of death or to study the changes caused by disease

Which of the following is not used to classify epithelial tissues?
A. Matrix
B. Structure
C. Function
D. Location

D. Location

epithelium characteristics

A. made almost entirely of tightly packed cells (not much matrix)
B. Covers body surfaces and forms glands (skin, digestive tract, respiratory tract, heart and blood vessels, many body cavities)
C. Most have a free and a basal surface (lateral surface is in between cells)
D. Basement membrane
E. Avascular
F. Capable of regeneration mitosis

T or F: Epithelium cannot undergo mitosis because it is avascular.

False

What is the basement membrane of an epithelial cell?

an extracellular material formed by secretions from epithelial and connective tissue cells

What does the basement membrane do?

1. helps attach epithelial cells to the underlying connective tissues
2. guides cell migration for tissue repair
3. filters (in the nephrons of the kidney)

Do all epithelium cells have a basement membrane?

No

the function of epithelial tissues

(Before you go, Don't Forget Some Apples Peel)
Barrier, Diffusion, Filtration, Secretion, Absorption, Protection

the free surface of an epithelial cell can be/have: (and what do they do?)

1. Smooth to reduce friction (blood vessels)
2. Microvilli/brush border to increase surface area for absorption or secretion
3. Cilia to move materials across the cell surface

simple squamous epithelium locations

lining of blood vessels & heart, lymphatic vessels (endothelium), and alveoli of lungs

function of simple squamous epithelium

diffusion (oxygen in lungs), filtration (kidneys), some secretion, some protection

simple cuboidal epithelium locations

microvilli in kidney tubules & terminal bronchioles in lungs

functions of simple cuboidal epithelium

secretion & absorption

simple columnar epithelium locations

microvilli in GI tract & cilia in lungs

functions of simple columnar epithelium

secretion and absorption in intestine & particles out of bronchioles in the cilia in the lungs

stratified squamous epithelium locations

non-keratinized: mouth, throat, esophagus
keratinized: skin

non-keratinized stratified squamous epithelium

living cells in the deepest and outermost layers that are covered with a layer of fluid on the outer layer (they are moist)

keratinzed stratified squamous epithelium

living cells in the deepest layers, and dead cells containing the protein keratin in the outer layers (they are dry, durable, and moisture-resistant)

functions of stratified squamous epithelium

protection from abrasion, chemicals, water loss, and infection

stratified cuboidal epithelium locations

sweat gland ducts

functions of stratified cuboidal epithelium

secretion, absorption, & protection against infection

stratified columnar epithelium locations

mammary gland duct, larynx, portion of male urethra

function of stratified columnar epithelium

secretion and protection

pseudostratified columnar epithelium characteristics

almost always ciliated, have goblet cells, & are mucous

pseudostratified columnar epithelium locations

nasal sinuses, bronchi of lungs, trachea

functions of pseudostratified columnar epithelium

secrete and move mucus

transitional epithelium locations

lining of urinary bladder and ureters

functions of transitional epithelium

stretch with volume changes of organ & protects against caustic effects of urine

transitional epithelium shape

cube when not stretched, squamous when stretched

cell connectors

desmosomes (& Hemidesmosomes), tight junctions, adhesion belts, gap junctions

function of a desmosome

bind cells together

function of a hemidesmosome

bind cells to basement membrane

function of a tight junction

holds cells together & forms a permeability layer

function of an adhesion belt

help the tight junctions anchor the epithelial cells to each other

function of a gap junction

intercellular communication

endocrine glands

secrete hormones directly into the bloodstream (no ducts), which means its secretions are separated from the epithelium of origin

exocrine glands

has ducts, which means its secretions maintain open contact with the epithelium from which it developed

goblet cells

unicellular glands that secrete mucus

How are multicellular exocrine glands classified?

the structure of their ducts or by their method of secretion

T or F: most glands are multicellular

true

simple structure glands

ducts with a few branches

compound structure glands

ducts with many branches

tubular structure glands

secretory regions shaped like tubes

acinar (alveolar) structure glands

sac-like structures

merocrine secretion

no loss of cellular material (like sweat)

apocrine secretion

part of cell pinches off (like mammary glands)

holocrine secretion

whole cell is part of secretion (like sebaceous gland)

T or F: connective tissue is found in every organ.

true

functions of connective tissue, and examples of connective tissues that do those things

1. enclose/encapsulate organs (ex: muscles, arteries, veins)
2. connect tissues (ex: tendons and ligaments)
3. support and movement (ex: bones provide rigid support)
4. storage (ex: fat stores high energy molecules, bone stores minerals like Ca and P)
5. cushion/insulation (ex: fat)
6. transport (ex: blood)
7. protection (ex: immune system cells, bones)

what connective tissue function does the word stem "blast" identify?

create matrix

what connective tissue function does the word stem "cyte" identify?

maintain matrix

what connective tissue function does the word stem "clast" identify?

break down matrix (for remodeling)

types of connective tissue cells

1. adipose/fat cells (adipocytes)
2. mast cells - contain heparin, histamine, and proteolytic enzymes & are released in response to injury/infection
3. white blood cells - respond to injury/infection as well
4. macrophages - phagocytize to provide protection (can be fixed or wandering
5. undifferentiated mesenchyme (stem cells)

What are the 3 parts of the extracellular matrix of connective tissue?

protein fibers, ground substance, & fluid

3 different types of protein fibers of the matrix of connective tissue

collagen, reticular, & elastic

collagen protein fiber characteristics

most common protein in the body (approx. 6% of body weight) & very strong and flexible but very inelastic

reticular protein fiber characteristics

these are fine collagen fibers that form a branching network and fills spaces between tissues and organs & it is not as strong as most collagen fibers

elastic protein fiber characteristics

returns to original shape

ground substance of connective tissue extracellular matrix

the shapeless background in a microscope

3 types of ground substance in the matrix of connective tissue

hyaluronic acid, proteoglycans, & adhesive molecules

hyaluronic acid

a polysaccharide that is the lubricant for joint cavities

proteoglycans

protein + polysaccharide that traps large amounts of water and provides cartilage with its resilient nature

adhesive molecules

hold proteoglycans together

What is the component that is not part of the extracellular matrix of Connective Tissues?
A. Fluid
B. Protein fibers
C. Holocrine tissue
D. Ground substance

C. Holocrine tissue

loose (areolar) connective tissue

the loose packing material of most organs and tissues that attaches skin to underlying tissues

dense regular connective tissue

has abundant collagen fibers and resists stretching

tendons

muscle to bone

ligaments

bone to bone

dense irregular collagenous connective tissue

has collagen fibers that are randomly oriented and is tough

what connective tissue makes up most of the dermis of the skin, as well as scars?

dense irregular collagenous connective tissue

What tissue makes up the epidermis?

stratified squamous epithelium

What tissue makes up the dermis?

dense irregular collagenous CT

What tissue makes up the hypodermis (subcutaneous)?

loose (areolar) CT

adipose tissue

made of adipocytes, and can be yellow/white or brown

yellow/white adipose tissue

Most abundant type and is white at birth then yellows with age

brown adipose tissue

in axillae and neck and is more abundant in babies

reticular tissue

provides a super structure for lymphatic and hemopoietic tissues like lymph nodes, spleen, and bone marrow, & the spaces in between cells contain white blood cells and dendritic cells

cartilage characteristics

firmest structure in the body except bone, avascular, no blood/nerve supply, and heals very slowly

perichondrium

dense irregular connective tissue that surrounds nearly all cartilage and secretes cartilage cells

When do cartilage cells become chondrocytes?

when surrounded by the matrix and are located in spaces called lacunae

the 3 types of cartilage

hyaline, fibrocartilage, elastic

hyaline cartilage structure

collagen fibers and proteoglycans in the matrix

hyaline cartilage locations

where strong support and some flexibility is needed (rib cage, trachea, bronchi), on articulation surfaces, embryo skeletons, & bone growth zones

fibrocartilage structure

thick collagen fibers in matrix that are slightly compressible and tough

fibrocartilage locations

areas of pressure on joints (knees, interverbal disks)

elastic cartilage structure

elastic and collagen fibers and proteoglycans in the matrix that are rigid but elastic

elastic cartilage location

external ears

bone

hard connective tissue made of osteocytes (living cells) + mineralized matrix

bone matrix

provides strength/rigidity and is made up of organic collagen fibers and inorganic hydroxyapetite (Ca++ and PO4)

Where are bone osteocytes located?

in lacunae

types of bone

cancellous/spongy bone & compact bone

cancellous/spongy bone

trabeculae of bone with spaces that is found inside the bone, skull, vertebrae, sternum, and ends of long bones

compact bone

concentric layers around a central canal and is around the periphery of the bone

blood matrix

liquid/fluid plasma (lacks fibers) that allows materials like food, oxygen, and waste products to move quickly through the body

formed elements in blood

red cells, white cells, & platelets