CELLS & TISSUE

Cells

1600’s: Robert Hooke The Cell Theory

All living things are made up of cells The cell is the basic unit of structure & function of

all living things All cells come from pre-existing cells

Review of Cells

C, O, H, N Interstitial fluid

Made from blood All exchgs bt cells &

blood made thru this fluid

Nucleus Plasma membrane Cytoplasm

Review cont:

Cytosol Mitochondrion Ribosome ER

Smooth rough

Golgi apparatus Lysosome Secretory vesicles Cytoskeleton Centrioles Cilia flagella

Cell Diversity

Connect body parts Fibroblast

Elongated Lies along the cable-like

fibers that it secretes Has lots of RER & GA to

make & secrete protein bldg blocks of these fibers

Erthrocyte (RBC) Carries O2

Concave disc=↑ SA Streamlined = flows easily So much O-carrying

pigment is packed in that all other organelles have been removed to make room

Cells that:

Covers & lines organs Epithelial cells

Hexagonal Pack together well Many intermediat

filaments wc resist tearing when rubbed/pulled

Move organs & body parts Skeletal muscle &

smooth muscle cells Elongated Filled w/ contractile

filaments Shorten Move bones Change size of organs

Cells that:

Store nutrients Fat cells Large & round From lg lipid droplet in

cytoplasm Fight disease

Macrophage (phagocytic cell) Long pseudopods sent out

to infection Has many lysosomes wc

digest infectious microorgs

Cells that:

Gather info & controls body functions Nerve cell

Very long Receives & transmits to other

parts of body Covered w/ lg plasma membr Many rER to make parts of

membr

Are for reproduction Oocyte (f)

Lgst cell Has many copies of all organells

to distribute to daughter cells Sperm (m)

Long, streamlined for “swimming”

Flagellum to propel

Cells that:

Body Tissues Epithelial Tissue

(epithelium) lining, covering &

glandular tissue Glandular epithelium forms

glands Lining & covering epith

covers all free body surfaces Contains versatile cells

intestine

Can form outer layer of skin Almost all subs that

body give/receives must go thru epith

Can dip in to line cavities Functions:

Protection Absoption Filtration Secretion

kidney

Special Characteristics Fit close together, forming sheets Bound together at many pts by

cell junctions (desmosomes & tight junctions)

Has an apical surface (unattached) Slick, smooth, microvilli, cilia

Has a basement membr (lower surface) Secreted by both epithel cells &

connective tissue cells next to it Avascular (lack own blood

supply) Depends on diffusion from

capillaries for nutrients & O2

Easily self regenerates

Classification of Epithelium 2 names First: = number of cell

layers it has Simple epith= one layer Stratified epith=more

than one cell layer Second = describe the

shape of its cells Squamous = flat Cuboidal = cube Columnar = columns

Stratified epith named for apical surface

Simple Epithelia

Thin layer ≠ protection =absorption, secretion, filtration Simple Squamous

Rests on basement layer Air sacs Walls of capillaries

Simple Cuboidal Rests on basement layer In glands and ducts Salivary glands, pancreas, walls of

kidney tubules, surface of ovaries Simple Columnar

Tall Goblet cells

Product lubricating mucus

Entire length of digestive tract (stomach to anus)

Line body cavities open to body exterior = mucosae/mucus membranes

Pseudostratified columnar Rests on basement membr

BUT: some cells shorter than others Nuclei at diff heights False impression that it is stratified

Absorption/secretion Ciliated variety =

lines resp tract Goblet cells traps

dust/debris

Stratified Epithelia More durable = protection

Stratified Squamous Most common strat epith Apical = squamous Basement memb = cub or

col Subject to abuse/friction

Esophagus, mouth, outer skin

Stratified Cuboidal Usually just 2 layers At least apical cells cub

Stratified Columnar Apical cells col Basal cells vary in size

& shape

Both fairly rare Mainly in ducts of lg

glands

Transitional Epithelium Highly modified

stratified squamous epith

Forms lining of only few organs

Urinary bladder, ureters & parts of urethra

Subject to considerable stretching

Basal layer cub or col Apical cells vary

Not Stretched = membr many layered, surface cells rounded/domed

Stretched = (w/urine) epith thins, surface cells flatten & become squamous-like

Allows cells to slip past ea other & chg shape (=transition)

Glandular Epithelium Gland=make & secrete a specific product = secretion 2 Major Types of Glands

Endocrine glands Lose connection to surface (duct) =

ductless All hormones Secretions diffuse directly into blood

vessels Thyroid, adrenals & pituitary

Exocrine Glands Have ducts where

secretion occurs to surface

Sweat & oil glands, liver & pancreas

Both internal & external

Connective Tissue

Connects body parts Everywhere, most

abundant & distributed tissue

Protecting, supporting & binding together other body tissues

Characteristics

Variations in blood supply Most well vascularized

Tendons & ligaments = poor blood supply

Cartilages = avascular = slow to heal

Would you rather break a bone or tear a ligament?

Extracellular Matrix made of many diff types of cells & varying amts of nonliving

substance outside the cells = extracellular matrix

Extracellular Matrix Made by CT then secreted to outside 2 main elements

Structureless ground substance fibers

Ground substance = mostly water plus adhesion proteins (“glue”) and lg charged polysaccharide molecule (will trap water as they intertwine)

Matrix can be very fluid, gel-like, firm, rock hard

Fibers = various types & amts Include: collagen = white, hi tensile strength Elastic = yellow Reticular = fine collagen fibers wc form internal “skeleton”

of soft organs (spleen)

Due to the extracellular matrix, connective tissue is able to form soft packaging

tissue around organs bear weight w/stand stretching w/stand abuse/abrasion

w/c other tissues couldn’t

Variations of connective tissue

One extreme to another Fat tissue = many cells, matrix

is soft Bone & cartilage = few cells,

very hard matrix (strong)

Types of Connective Tissue

Bone (osseous) = bone cells in lacunae (pits) surrounded by very hard matrix matrix contains Ca salts & lg amts of collagen fibers Excellent protection & support

Cartilage =less hard, more flexible only in a few places most common = hyaline cartilage (glassy)

Many collagen fibers in rubbery matrix Forms supporting structures

Larynx Ribs to breastbone Ends of bones at joints

Fetus = mostly hyaline, replaced by bone by birth

Fibrocartilage Highly

compressible Disks bt vertebrae

Elastic cartilage ear

Dense Connective Tissue Main matrix element = collagen fibers (in rows

w/fibroblasts) Forms strong rope-like structures

Tendons (m2b) Ligaments (b2b)

More elastic/stretchy

Lower layer of skin (dermis) = in sheets

Loose CT Softer More cells, fewer fibers (except blood) Areolar tissue

Soft/cobwebby Cushions/protects organs ‘glue’ wc holds organs in their positions Fluid matrix w/all types of fibers Appears to be empty space A resevoir of water & salts for all other cells to get nutrients and dispose of

“wastes”

Adipose tissue Reticular CT

Adipose tissue Fat Mostly oil… pushes

nucleus to one side Beneath skin Insulates/protects Kidneys surrounded Cushions eye in socket For fuel if needed Reticular CT

Interwoven reticular fibers Limited sites: stroma to

support free blood cells in lymph nodes, spleen, bone marrow

Loose connective tissue types Reticular connective tissue

Delicate network of interwoven fibers Forms stroma (internal supporting network) of lymphoid organs

Lymph nodes Spleen Bone marrow

Blood (vascular tissue) Blood cells surrounded by fluid matrix called blood plasma Fibers are visible during clotting Functions as the transport vehicle for materials

Muscle Tissue Function is to produce movement Three types

Skeletal muscle Cardiac muscle Smooth muscle

Muscle Tissue Types

Skeletal muscle Under voluntary control Contracts to pull on bones or skin Produces gross body movements or facial expressions Characteristics of skeletal muscle cells

Striated Multinucleate (more than one nucleus) Long, cylindrical

Cardiac muscle Under involuntary control Found only in the heart Function is to pump blood Characteristics of cardiac muscle cells

Cells are attached to other cardiac muscle cells at intercalated disks Striated One nucleus per cell

Smooth muscle Under involuntary muscle Found in walls of hollow organs such as stomach, uterus, and

blood vessels Characteristics of smooth muscle cells

No visible striations One nucleus per cell Spindle-shaped cells

Nervous Tissue

Composed of neurons and nerve support cells Function is to send impulses to other areas of the body

Irritability Conductivity

Tissue Repair (Wound Healing)

Regeneration Replacement of destroyed tissue by the same kind of cells

Fibrosis Repair by dense (fibrous) connective tissue (scar tissue)

Determination of method Type of tissue damaged Severity of the injury

Events in Tissue Repair

Capillaries become very permeable Introduce clotting proteins A clot walls off the injured area

Formation of granulation tissue Growth of new capillaries Rebuild collagen fibers

Regeneration of surface epithelium Scab detaches

Regeneration of Tissues

Tissues that regenerate easily Epithelial tissue (skin and mucous membranes) Fibrous connective tissues and bone

Tissues that regenerate poorly Skeletal muscle

Tissues that are replaced largely with scar tissue Cardiac muscle Nervous tissue within the brain and spinal cord

Developmental Aspects of Tissue

Epithelial tissue arises from all three primary germ layers Muscle and connective tissue arise from the mesoderm Nervous tissue arises from the ectoderm With old age, there is a decrease in mass and viability in

most tissues