Cells and Tissues Pt. III Chapter 3 Pages 87-104.

Cells and Tissues Pt. IIIChapter 3Pages 87-104

Tissues

Groups of cells similar in structure and function

Four types:◦ Epithelial - covering◦ Connective - support◦ Nervous - control◦ Muscle – movement

Each organ is comprised of a specific arrangement of these tissue types◦ The tissues determine

the organ’s structure and function

Epithelial Tissue

Epithe = laid on, covering◦ This is the lining, covering and glandular

tissue of the bodyFunctions: protection, absorption,

filtration and secretion

Special Characteristics of EpitheliumEpithelial cells are bound tightly together

(with few exceptions) by membrane junctions

One side of the cell membranes is unattached (free) – this side is the apical surface and is the exposed surface

The lower surface of epithelium rests on a basement membrane – a mixture of structural proteins and supports secreted by the epithelium and connective tissue right below the epithelium

Avascular – depends on diffusionEasy regeneration if well nourished

Classes of EpitheliumSimple

epithelium◦ Squamous◦ Cuboidal◦ Columnar

Stratified epithelium◦ Squamous◦ Cuboidal◦ Columnar

Classes of Epithelium DetailsSimple squamous – thin cells on

basement membrane◦Usually site of filtration or rapid

diffusion◦Ex: Capillaries and lung alveoli◦Also forms serous membranes

(serosae)Simple cuboidal – common in

glands and ducts◦Also in tubule walls and covering of

ovaries

Simple Epithelium Pictures

Simple Squamous Epithelium Simple Cuboidal Epithelium

Classes of Epithelium Details Cont. Simple columnar epithelium – single

layer of tall cells◦Often contains goblet cells (produce

mucus)◦Lines entire digestive tract; stomach to

anus◦Mucosae (mucous membranes) line

body cavities open to the body exteriorPseudostratified columnar – all cells

rest on the basement membrane but are different heights, thus looking stratified◦Found in respiratory tract

Simple Epithelium Pictures II

Simple Columnar Epithelium Pseudostratified Epithelium

Classes of Epithelium Details Cont.Stratified Squamous –

several layers of cells, those at the free edge are squamous, those close to the basement membrane are cuboidal or columnar◦ Found in places that suffer

mechanical abuse◦ Esophagus, skin etc.

Stratified cuboidal and columnar are rare in the body◦ Stratified cuboidal usually

two cells thick and found in ducts of large glands

Classes of Epithelium Details Cont.Transitional Epithelium

– stratified squamous that lines few organs◦ The bladder, ureters and

part of urethra◦ Basement cells are

cuboidal◦ Apical cells vary; when

the organ is stretched, they are flattened, slide over each other and become squamous

◦ When the organ is relaxed, the apical cells appear stratified and rounded cuboidal

Classes of Epithelium Details Cont. Glandular epithelium – glands secrete products called

secretions◦ Secretions are mostly proteins in aqueous fluid◦ Secretion is active thus the cells require high level of

materials from the bloodEndocrine glands – are ductless and secretions

diffuse directly into the bloodExocrine glands – have ducts and secrete to the

epithelial (often luminal) surface

Did you get it?

1. What two criteria are used to classify epithelial tissues?

2. How do endocrine and exocrine glands differ in structure and function?

3. Which of the following properties apply to epithelial tissues? Has blood vessels, can repair itself, cells have specialized cell junctions.

Connective TissueConnects body partsFunctions: protecting, supporting

and binding together other body tissues

Common characteristics:◦Most CT is vascularized

Exceptions: Ligaments, tendons, cartilage

◦Extracellular matrix Non-living substances outside the cells

Extracellular matrixProduced by the CT cells then secretedTwo main elements:

◦ Ground Substance – mostly water, some adhesion proteins (glue) and polysaccharides The proteins allow the cells to attach themselves to the

matrix fibers, the polysaccharides trap water and make the matrix “gel-like”

◦ Fibers – vary in type and amount Collagen (white) Elastic (yellow) – can stretch and recoil Reticular fibers – fine collagen fibers that form the

“skeleton” of soft organs The fiber monomers are secreted by the CT cells

Varied amounts of ground substance and fibers determine the amount of stress and organ can bear

Ground Substance and Fibers

CT - BoneOsseous tissue

made of osteocytes in lacunae

Bone cells are surrounded by hard matrix contain calcium salts and collagen fibers

CT - Cartilage More flexible and less hard than bone

Major cell type is chondrocytes

Types:◦ Hyaline

cartilage Covers ends of

bones, forms support structures of certain organs

◦ Fibrocartilage Withstands high

stress and impact

◦ Elastic cartilage Ex: external ear

Dense CTA.k.a. – dense fibrous tissueMain feature – smooth, uniform collagen fibersMain cell type – fibroblastsForms tendons (muscle to bone) and ligaments

(bone to bone)◦ Ligaments are stretchier than tendons

Also forms lower layers of dermis

Loose CT - AreolarSofter with more cells and

few fibersAreolar Tissue – cobwebby

tissue◦ Cushions and protects soft

organs◦ Acts as glue to hold organs

together◦ Sub-epithelial layer is called

the lamina propria◦ Forms a reservoir of

extracellular fluid◦ When a body part becomes

inflamed, this area swells with water Edema

◦ Contains wandering phagocytes

Loose CT - AdiposeFat tissueMain cell –

adipocyte, which has a large lipid droplet and a compressed nucleus near the plasma membrane◦ These cells

sometimes called “signet ring cells”

Insulation and protection of the body

Loose CT - ReticularMain cell type – reticular cells which produce a

woven network of extracellular reticular fibersSimilar to fibroblasts but limited to locationForms the stroma (bed) or framework of

organs with free blood cells◦ Ex: lymph nodes, spleen, marrow

CT - BloodVascular tissue – consists of blood cells

surrounded by non-living fluid matrix called plasma

The fibers of the blood are proteins that only become visible during clotting

Did you get it

1. How do connective tissues differ from other tissues?

2. John wants to become a professional basketball player but he is short for his age. Unfortunately his epiphyseal plates have already fused. Why is this unfortunate for John?

Muscle Tissue - Movement

Muscle Tissue - SkeletalPackaged by sheets of CT

into skeletal muscles, which are attached to bones

Also called Voluntary muscle or striated muscle

When these muscles contract, bones and skin are moved◦ Allows gross body

movements ◦ Allows facial expression

Individual muscle cells are called muscle fibers◦ Each is multinucleated and

can be many inches long

Muscle Tissue - CardiacStriated like skeletal

muscleUninucleated cells,

somewhat short, and branched

Fit together at junctions called intercalated discs◦ Discs contain gap

junctions for electrical conduction and uniform contraction

Involuntary

Muscle Tissue - SmoothAlso called visceral muscle InvoluntaryNo striations, short, spindle-shaped cells, uninucleateFound in walls of hollow organs

◦ Constricts when contracted◦ Dilates when relaxed

Contracts slowlyPeristalsis = special contraction for propulsion of food

Nervous Tissue Neurons – main cell type

◦ Receive and conduct electrochemical impulses Irritability Conductivity

Cell extensions may be 3+ feet long, allows information to travel long distances quickly

Support cells in groups are called neuroglia◦ Insulate, support, protect neurons

Did you get it?

1. Which muscle type(s) is injured when you pull a muscle while exercising?

2. How does the extended length of a neuron’s processes aid its function in the body?

Part III: Developmental Aspects of Cells and Tissues

Most cells undergo mitosis until puberty (except neurons)◦ Once adult stature has been reached, most cells stop

dividing Become amitotic Ex: heart muscle cells

Cells that continue to divide:◦ Skin and intestinal cells

Some cells only divide for tissue regeneration◦ Ex: liver

The cause of aging is still undetermined◦ Chemical insults to cells◦ Exposure to environmental factors◦ Genetic programming◦ Disuse of tissues

Developmental Aspects Cont.As the body ages, tissues lose quality

◦ Epithelium more easily damaged◦ Glands become less active◦ We “dry out,” less mucus, oil and sweat production◦ Connective tissues change

Bones become porous Tissue repair slows Decreased circulatory system efficiency

Abnormal proliferation results in cell masses called neoplasms (tumors)◦ May be benign or malignant (cancerous)

Hyperplasia is an increase in cell number within an organ that is not neoplastic◦ Ex: Breast tissue during pregnancy

Atrophy – is loss of tissue size or cell number◦ Occurs with lose of nutrient supply or nerve supply

Did you get it?

1. Which of the four types of tissue is most likely to remain mitotic throughout life?

2. What is a neoplasm?3. How does the activity of

endocrine glands change as the body ages?