Tissues

What are epithelial cells tied together by

What are epithelial cells tied together by

- tight junctions

- desmosomes

What is the brush border?

- the microvilli are often so dense that the cell apices have a fuzzy appearance called a brush border.

Can epithelial cells regenerate?

Yes, they can reproduce rapidly

What does the basement membrane consist of?

- Basal lamina

- reticular lamina

What is the position of reticular lamina to the basal lamina

Reticular lamina is deep to the Basal lamina

Do epithelial tissues contain blood vessels and nerves?

They are avascular and innervated

Types of epithelial tissues based on number of layers

- simple

- stratified

description of stratified epithelium

- several layers of cells

- commonly present in areas with high abrasion rate

- cell shape differs in different layers

- named according to the cells in the apical surface

Steps for preparing light microscope slide

- fixed (preserved)

- cut into think sections

- stained with coloured dyes

Steps for preparing electron microscope slide

- fixed (preserved)

- cut into think sections

- stained with heavy metal salts

Image produced by TEM vs SEM

2D image vs 3D image

2 forms of epithelial tissue in the body

- covering and lining epithelium

- glandular epithelium

Functions of epithelial tissue

- protection

- absorption

- filtration

- excretion

- secretion

- sensory receptors

Polarity of epithelial tissue

- Apical surface (not attached to surrounding tissue and is exposed)

- Basal surface ( attached to underlying connective tissue)

Where are microvilli found in epithelial cells?

apical surface of epithelial cells

Where is the basal lamina found

Adjacent to the Basal surface

description of basal lamina

- thin supporting layer

- contains glycoproteins and collagen fibres

function of basal lamina

- Acts as a selective filter ( determines which molecules enter epithelial tissues from underlying connective tissue)

- Acts as a scaffolding ( epithelial cells can migrate to and repair wounds)

Types of epithelial cells

- squamous

- cuboidal

- columnar

Description of simple squamous epithelium

- single layer of flattened cells

- disc shaped nuclei

function of simple squamous epithelium

- allow diffusion of substances where protection is unimportant

- secretes lubricating substance in serosae ( lining of ventral body cavity)

Location of simple squamous epithelium

- Kidney glomeruli

- air sacs of lungs

- lining of blood vessels

- lining of lymphatic vessels

description of simple cuboidal cells

- Single layer of cube like cells

- spherical central nuclei

Function of simple cuboidal epithelium

secretion and absorption

location of simple cuboidal epithelium

- Kidney tubules

- ducts

- secretory portions of small glands (thyroid etc.)

- ovary surface

description of simple columnar epithelium

- single layer of tall cells

- round/oval nuclei

- many bear microvilli

- some bear cilia

- may contain goblet cells

function of simple columnar epithelium

- absorption

- secretion of mucus and enzymes

location of simple columnar epithelium

- non ciliated lines most of digestive tract and gallbladder, excretory ducts

- ciliated lines small bronchi and uterine tubes (oviduct, fallopian tube), uterus

Description of Pseudostratified Columnar Epithelium

- Single layer of cells which differ at different heights

Function of Pseudostratified columnar epithelium

- secret substances such as mucus

location of pseudostratified columnar epithelium

- non ciliated type in the male sperm carrying ducts, large gland ducts

- ciliated in the trachea, upper respiratory tract

What are the 2 types of simple squamous epithelial cells

- Endothelium (slick with low friction present in lymphatic vessels , hollow organs in cardiovascular system)

- mesothelium ( epithelium found in serous membranes and membranes lining the ventral body cavity)

Description of stratified squamous epithelium

- multilayer of cells with several cell types

- basal cells are cuboidal or columnar epithelium while surface is squamous

- basal cells active in mitosis

function of stratified squamous epithelium

Protect tissues in areas subjected to abrasion

location of stratified squamous epithelium

- non keratinized present in mouth, oesophagus and vagina (wet)

- keratinized present in skin (dry)

description of transitional epithelium

- Basal cells contain columnar or cuboidal cells

- Surface cells either dome shaped or squamous depending on degree of stretch

Function of transition epithelium

Stretches readily as it allows stored urine to distend urinary organ

location of transitional epithelium

Urinary bladder, ureter and part of urethra

What is a secretion

a water based fluid that usually contains proteins while some release lipids or steroid secretions

How are glands classified?

- either endocrine (internally secreting) or exocrine (externally secreting)

- either unicellular or multicellular

Unicellular glands Vs Multicellular glands

- Unicellular are single celled glands scattered within epithelial cells

- multicellular contain many cells and are formed by inward growth of an epithelial sheet into underlying connective tissue

Endocrine glands Vs exocrine glands

- Exocrine glands retain connecting cells and form ducts

- Endocrine glands lose the connecting cells and are "ductless" therefore release hormone into the interstitial fluid which then enters the blood

where are stratified cuboidal epithelium found?

ducts of some glands (mammary, sweat)

Where are stratified columnar epithelium found?

pharynx and male urethra

Examples of exocrine glands

mucous, sweat, oil, and salivary glands

structural classification of multicellular exocrine glands

Classification of multicellular exocrine glands by mode of secretion

- merocrine ( releases substance by exocytosis)

- holocrine ( releases substance and dead fragments by cell rupturing)

- apocrine ( pinches off portion of cells and cell heals itself)

Types of connective tissue

- connective tissue proper

- Bone

- cartilage

- blood

functions of connective tissue

- binding and support

- protection

- insulation

- storing reserve fuel

- transporting substances

common characteristics of connective tissue

- contain extracellular matrix

- have a common origin, they arise from embryonic mesenchyme

What are the main components of connective tissue

- ground substance

- fibres

- cells

Components of the ground substance of connective tissue

- Interstitial fluid ( contains large amounts of fluid which allows dissolved substances to fuse between blood and cells)

- cell adhesion proteins ( allows connective tissue cells to attach to the extracellular matrix)

- proteoglycans ( consists of protein core to which GAG's attach to it and controls viscosity)

Three types of connective tissue fibres

- Collagen fibres (strongest and most abundant)

- elastic fibres

- reticular fibres

Types of connective tissue cells

- Fibroblasts in CT proper which become fibrocytes

- Chondroblasts in cartilage which become chondrocytes

- Osteoblasts in bones which become osteocytes

Cell types which are found within the connective tissue

- Adipocytes (fat cells)

- white blood cells

- Mast cells ( detect foreign microorganisms and initiate an inflammatory response, contains histamine, heparin, proteases and other enzymes )

- macrophages

purpose of heparin and histamine

- heparin : an anticoagulant chemical that prevents blood clotting when free in the bloodstream

- histamine: a substance that makes capillaries leaky

types of connective tissue proper

- Loose ( areolar, adipose, reticular)

- Dense ( regular, irregular, elastic)

Description of Areolar Connective Tissue

- gel like matrix containing all 3 fibre ( collagen, reticular and elastic) types as well as containing the cells, fibrocytes, macrophages, mast cells and WBC's

function of areolar connective tissue

- wraps and cushions organs

- phagocytize bacteria

- involved in inflammatory response

- holds and conveys tissue fluid

location of areolar connective tissue

- Under epithelia ( forms lamina propria of mucus membrane)

- surrounds capillaries

- packages organs

Description of Adipose Connective Tissue

- gel like matrix containing closely packed adipocytes

Function of Adipose connective tissue

- provide reserve fuel

- provide insulation against heat

- support and protect organs

location of adipose connective tissue

- under skin in subcutaneous tissue

- around eyeball and kidney

- abdomen

- breast

What are white and brown fat cells?

White fat stores nutrients (mainly for other cells), but brown fat contains abundant mitochondria that use the lipid fuels to generate heat (instead of generating ATP molecules).

Description of Reticular Connective Tissue

- loose network of reticular fibres in a gel like substance

- main cell type is fibroblasts

function of reticular connective tissue

forms a soft internal skeleton which supports other cell types

location of reticular connective tissue

Lymphoid organs (lymph nodes, bone marrow, and spleen).

description of regular dense connective tissue

Primarily parallel collagen fibers, a few elastic fiber, major cell type is the fibroblast.

function of regular dense connective tissue

-Attaches muscles to bones/muscles

-Attaches bones to bones

-Withstands great tensile stress when pulling force is applied in one direction.

location of regular dense connective tissue

- tendons

- most ligaments

- aponeuroses

description of irregular connective tissue

- primarily irregularly arranged collagen fibres

- main cell type is fibroblasts

function of irregular connective tissue

- withstand tension from many different directions

location of irregular connective tissue

- Fibrous capsules of organs and of joints

- dermis of the skin

- submucosa of digestive tract.

description of elastic dense connective tissue

- dense regular connective tissue containing alot of elastic fibres

function of elastic dense connective tissue

- allows tissue to recoil after stretching

- maintains pulsatile flow of blood through arteries; aids

- passive recoil of lungs following inspiration

location of elastic dense connective tissue

- walls of large arteries

- walls of bronchial tubes

Description of Hyaline connective tissue

- amorphous but firm matrix

- chondrocytes made in matrix and lie in lacuna when theyre mature

function of Hyaline connective tissue

- supports and reinforces

- resists compressive stress

- serves as a resilient cushion

location of Hyaline connective tissue

- forms costal cartilage of ribs

- forms cartilage of nose, trachea and larynx

- forms most of the embryonic skeleton

- covers ends of long bones in joint cavities

description of elastic cartilage connective tissue

- similar to hyaline but contains more elastic fibres

function of elastic cartilage connective tissue

- maintains the shape of the structure while maintaining good flexibility

location of elastic cartilage connective tissue

- external ear

- epiglottis

description of fibrocartilage

- matrix similar to hyaline but less firm

- thick collagen fibres predominate

function of fibrocartilage

- tensile strength allows it to absorb compressive shock

location of fibrocartilage

- intervertebral discs

- pubic symphysis

- discs of knee joint

description of bone tissue

- hard calcified matrix with alot of collagen fibres

- osteocytes lie in lacunae

- very well vascularized

description of blood

RBC and WBC in a fluid matrix

Function of blood

Transports respiratory gases, nutrients, wastes, and other substances

location of blood

within blood vessels

description of skeletal muscle tissue

- long cylindrical and multinucleate

- contains obvious striations

- poor regeneration

function of skeletal muscle tissue

- voluntary movement

- locomotion

- manipulation of the environment

- facial expressions

location of skeletal muscle tissue

attached to bones

description of cardiac muscle tissue

- striated, branching and uninucleate

- connects at intercalated discs

- no regeneration

function of cardiac muscle tissue

- as it contracts it propels blood into circulation

- involuntary control

location of cardiac muscle tissue

walls of the heart

description of smooth muscle

- cells are spindle shaped with central nuclei

- no striations

- cells are arranged closely to form sheet

- moderate regeneration

function of smooth muscle

- propels substances along internal passageways

- involuntary movement

Location of smooth muscle

Walls of hollow organs

Description of nervous tissue

- Neurons are branching cells

- cell processes that may be quite long extend from the nucleus-containing cell body

- also contributing to nervous tissue are non excitable supporting cells. (neurogelia)

Function of nervous tissue

- Neurons transmit electrical signals from sensory receptors and to effectors

- Supporting cells support and protect neurons.