Body Tissues

Tissue

group of cells with a similar structure and common function

Epithelial

covering

connective

support

muscle

movement

nervous

control

Epithelium

sheet of cells that cover a body surface or line a cavity/forms boundaries between different environments. Skin separates body tissues from the environment and dinner linings of the bladder, stomach, and lungs.

Functions of epithelium

Protect, absorb, filtrate, excrete, secrete, and sensory reception

cellularity

Composed of tightly packed cells

Specialized contacts

Tight Junctions and desmosomes they are like snaps and hooks that hold adjacent cells tightly together and prevent molecules from passing between them

Polarity

each epithelial cell has 2 surfaces apical surface, and basal surface

Apical surface

The exposed surface (air,liquid,etc..)

Basal Surface

The attached surface

Basement Membrane

Composed of 2 layers (basal lamina and reticular lamina) not made of cells, boundary between epithelium and connective tissue, and reinforced epithelium by resisting stretching and tearing.

Basal Lamina

Adhesive sheet at the basal surface of epithelium. sticky and filters material from below.

Reticular lamina

Thin layer of collagen fibers at superficial surface of connective tissue

Innervated

Has nerves

Avascular

No blood vessels

How get O2 and Carbs?

Diffusion from blood vessels in the underlying connective tissue

Regeneration

Epithelium has a high regeneration capacity which means it makes more of themselves

Why does regeneration happen

You’re always losing epithelial cells from friction, damage, bacteria, and acid - but they’re replaced at the same rate you lose them

Microvilli

(some have) finger like extensions of the cell membrane function is to increase surface area = increased secretion or increased absorption

Cilia

(some have) small hair-like structures on outside of a cell to propel substances

Mobile cell

moves the cell (not in epithelium or humans)

Stationary cell

Moves other stuff along the exterior of the cell (ex- egg in Fallopian tubes/mucus in trachea)

Classification of epithelium

Based on cell shape and arrangement

Simple

single layer of cells

Stratified

two or more layers of cells

squamous

Flat and scalelike

Cuboidal

Boxlike

Columnar

Tall and column shaped

When viewed from the top, all epithelial cells are…

6 sided (hexagon) and fit very tightly with their neighbors

Epithelial cells shape and order

Looks like honeycomb, and tight Junctions and desmosomes hold adjacent cells tight and do not allow stuff to pass between them

Why are hexagons stronger than boxes?

Fit tightly together with no gaps, attached to 6 other cells = stronger than 4, and joints are staggered and don’t line up=stronger

Connective tissue

Found everywhere in the body, and most abundant of the 4 tissue types

4 groups of CT in your body now

Connective tissue proper, cartilage, bone, blood

5 general functions of CT

Binding, support, protection, insulation, and transport of substances

All types of CT are derived from what during embryonic development

Mesenchyme

CT can be what regarding blood vessels?

Can be vascular/avascular/or anywhere in-between

CT is composed of 3 main elements

Ground substance (not alive), fibers (not alive), cells (alive)

Matrix

The nonliving parts of CT, composed of ground substance and fibers, bears weights, and withstands great and absorbs impact

Ground substance

Amorphous material that fills space between cells + contains fibers. and holds fluids

CT is a molecular sieve which means

Nutrients and other substances (O2,CO2) diffuse between the capillaries and the cells imbedded within it

Fibers

provide support (Collagen, Elastic, and Reticular)

Most abundant, made of fibrous protein (collagen) extremely strong - high tensile strength, and support for matrix

Collagen fibers

Made of a a fibrous protein elastin, allows stretching and recoils to original shape, more elastic fibers where CT expands and contracts EX - Blood vessels, and Lungs. Lots found in skin and elasticity decreases with age as the fibers wear out from use=wrinkles

Elastic fibers

Thin collagen-like fibers that branch out in between collagen fibers, branch out extensively like a spider web, and abundant where CT joins other tissues

Reticular Fibers

Blast

actively mitotic phase of a cell/secretes GS and fibers/Younger

Cyte

less active phase/a mature cell just doing its job/maintains the health of the matrix/if its area becomes injured, it reverts to a blast cell

Plasma cells

Produces antibodies (immune response)

Mast Cells

Detect foreign substances and initiates a local inflammatory response.

Macrophage

Phagocytizes foreign materials (bacteria,dust,junk) Engulfs dead cells+tissues and breaks them down (pac-man)

Mesenchyme

CT in the embryo that gives rise to the 4 other types of CT. None in your body right now!

Loose CT

cells are more spread out then in dense CT

Areolar CT

Located under the epithelium, and its function is to hold fluid in tissues = inflammation (swelling+bloating), and wraps and cushions organs

Adipose CT (fat)

Located under the skin/behind eyeballs/ and in breast and the function is to store reserved fuel/insulates against heat loss/some protection

Reticular CT

Location is lymphoid organs and function is it supports other cell types

Dense CT

Cells packed more tightly than loose CT

Tendons

attached muscle to bone

Ligaments

attach bone to bone

Dense regular CT examples

Tendons and ligaments both have great tensile strength

Dense irregular CT

Located dermis of skin/fibrous joint capsules and function is able to withstand tension exerted in many directions EX-Rotator cuff

Cartilage

Structurally between dense CT and bone, resists both tension and compression, tough but flexible, avascular/no nerves, heals slowly - avascular, less flexible as you age.

Perichondrium

well vasculized tissue that supplies oxygen and nutrients to cartilage cells

Hyaline cartilage

function is to support and reinforced and location is costal cartilage (skeleton)/external nose/ embryonic skeleton

Elastic cartilage

Function is maintains shape while allowing great flexibility and location is external ear

Fibrocartilage

Super strong and its function is great tensile strength/absorbs shock and pressure located in the inter vertebral discs / discs of knee joint

Bone

Hard-solid matrix with living cells throughout (absorbs calcium which makes it hard)

Blood

Liquid - filled matrix with living cells throughout

Fluid matrix in blood

Plasma

Nervous Tissue

No regeneration, parts are brain, nerves and the spinal cord. Composed of neurons and supporting neurons

Neurons

Generate and conduct never impulses

Supporting cells

Non conducting cells that support, protect, and insulate neurons

Muscle Tissue

Highly cellular and well vascularized

Skeletal Muscle

Function is voluntary movement, manipulation of environment, facial expressions and location is all skeletal muscles attached to bones or skin

Cardiac muscle

Cells contract pushing blood from the heart through the entire body and then back to the heart/involuntary. Location is the walls of the heart

Smooth muscle

Function is to propel substances or objects through internal passageways (food,urine,baby,etc) involuntary. location is the walls of hollow organs

Regeneration

Destroyed tissue is replaced by the SAME kind of tissue

Fibrosis

Destroyed tissue is replaced by SCAR tissue (fibrous CT)

3 steps of tissue repair

Inflammation - organization - regeneration or fibrosis

Inflamation

Injured cells release histamine and wound hormones that initiate tissue repair.

Capillaries dilate to do what?

brings WBC, plasma,clotting proteins + antibodies to the injured area which causes swelling.

Clotting proteins form

Blood clot

Blood clots happen to do what?

Stop the loss of blood, holds wounds ends together, and prevent penetration of bacteria or toxins

Scab

hardened outer portion of blood clot that is exposed to the air

Oragnization

New capillaries bud from nearby uninjured ones/must happen before all others can

Function of fibroblasts in organization process

Synthesize new collagen fibers to permanently connect the would ends together

What do macrophages do in the organization process?

digest the original clot and all the dead cells in the area

Blood clot becomes replaced by…?

granulation tissue (light pink), which releases a bacteria inhibiting substance

What kind of wounds is regeneration for

Minor to mild wounds

In regeneration how does surface epithelium regenerate?

epithelium cells migrate under the scab from the edges toward the center of the wound (how pieces of the scab fall off)

What kind of wounds is fibrosis for

more severe wounds

How does fibrosis work?

Epithelium regenerates just like regeneration, but the damaged tissue under the epithelium is replaced by fibrous CT which contracts and hardens as it matures

What does the fibrous CT in the process of fibrosis look like?

Visible under the epithelium as a scar

7 factors affecting tissue repair

type of tissue injured, type of injury,immediate care given, nutrition, blood supply,health, and age

What tissue heals the best

Epithelium

What tissue heals good

bone + fibrous CT

What tissue heals OK

Smooth muscle + dense regular CT

What tissue heals poor

Skeletal muscle + cartilage

What tissue heals the worst/not at all

Cardiac muscle + nervous tissue

In non-regenerating tissue and severe wounds, fibrous tissue replaces what

all lost tissue under the epithelium