tissues

tissue

collections of cells and cell products that perform specific, limited function

4 major or primary types of tissues

- epithelial
- connective
- muscle
- neural

functions of epithelial tissue

- covers exposed surfaces
- line internal passageways
- forms glands
- physical protection
- control permeability
- provide sensation
- produce secretions

extracellular matrix

nonliving, noncellular part of a connective tissue

functions of connective tissue

- fills internal spaces aka "packaging materials" of body
- supports other tissues (bone and cartilage)
- transports materials (blood and lymph)
- stores energy (fat or adipose tissue)

muscle tissues

specialized for contraction but do not actively stretch back out

muscle tissue divided into

skeletal, cardiac, smooth

skeletal muscle

voluntary; attached to bones

smooth muscle

found in walls of hollow organs

heart muscle

only in the heart

other names for neural tissue

nerve or nervous

function of neural tissue

carries electrical signals from one part of the body to another

different roles of epithelial tissue in the body

1. epithelia
2. glands

epithelia

layers of cells covering internal or external surfaces

glands

structures that produce secretion

characteristics of epithelium

- bound closely together by cell junctions
- polarity
- attachment
- avascularity
- regeneration is much faster in other tissue types

polarity

have a definite top and bottom

apical surface

top surface

basolateral surfaces

bottom or sides that attach to another cell or basement membrane

attachment

idea the epithelia are anchored to basement membrane/basal lamina

basement membrane/basal lamina

layer of extracellular material that attaches epithelia to underlying connective tissues and help form a barrier between

avascularity

lack blood vessels

microvilli

membrane extensions containing microfilaments

function of microvilli

increase surface area for absorption

columnar epithelial cells

cells that cover villi

cilia

hairlike structures that wave or beat

function of cilia

- moving or pushing materials over the epithelial surface
- absorption
- producing secretion

intracellular connections

- connect neighboring epithelial cells
- gives strength to epithelial tissue and helps cells communicate with each other

ways of having intracellular connection

1. interconnected by transmembrane proteins called cell adhesion molecules (CAMs)
2. cell junctions

types of cell junctions

- tight junctions
- gap junctions
- desmosomes

tight junctions

between apical portions of two neighboring cells that make a water-proof seal

purpose of tight junctions

ensures enzymes, acids, wates, etc. stay inside the lumen

gap junctions

- allow rapid communication between two connected cells
- two neighboring cells held together by channel proteins
- allows ions and small molecules to pass from cell to cell
- communication helps coordinating functions like beating of cilia

desmosomes

very strong structures that endure stretching and twisting and are present in superficial layers of skin

CAMs present in desmosomes

reinforced with intercellular cement and are anchored firmly into structure of cell

2 kinds of desmosomes

1. regular kind between two cells
2. hemidesmosomes

regular kind of desmosomes

spot and button desmosomes

hemidesmosomes

attached 1 cell to basement membrane

some roles for protein in the body

- enzymes
- structural proteins (collagen and keratin)
- antibodies

epithelia are classified by

cell shape and number of layers

types of shapes of epithelia

- squamous
- cuboidal
- columnar

simple epithelia

single layer of cells

stratified eipthelia

multiple layers

function of simple epithelia

good for absorption or area needing low protection

function of stratified epithelia

good for protection

germinative cells

epithelial stem cells that produce secretions

types of glands

endocrine and exocrine

endocrine glands

- duct-less
- products are secreted into body fluids

hormones

secretions from endocrine glands that circulate around body in blood stream

exocrine glands

release secretions into ducts that open onto an epithelial surface

examples of exocrine glands secretions

- sweat on skin
- tears
- mucus
- breast milk
- enzymes entering digestive tract

modes of secretion

- merocrine
- apocrine
- holocrine

merocrine secretions

- most common mode of secretion
- products released by vesicles into the ducts

secretory product

packaged into secretory vesicles and released from exocytosis

exocytosis

putting stuff out of cells

apocrine secretions

product is released when the apical portion of the cell pinches off and breaks

example of aprocrine secretion

mammary gland

holocrine secretions

- entire cell becomes packed with secretory product and then bursts
- cell gets replaced by germinative cells

example of holocrine secretion

sebaceous glands

types of secretions

- serous secretions
- mucuous
- mixed exocrine

serous secretions

watery solutions that contain proteins (usually enzymes)

example of serous secretions

gastric chief cells secrete stomach acid

mucuous secretions

glands secrete molecules called mucins

mucins

combine with water to form mucus

example of mucous secretions

various digestive glands produce mucus to protect the digestive tract from harsh digestive juices

goblet cells

only unicellular exocrine glands

mixed exocrine secretions

glands have more than one type of cells to produce serous and mucous products

example of mixed exocrine secretions

saliva

mesenchyme

embryonic tissue all connective tissue arises from

three parts of connective tissue

- specialized cells
- extracellular protein fibers
- fluid extracellular ground substance

what makes up the matrix of connective tissue

extracellular protein fibers and ground substance

ground substance

generally thicker and stickier than usual fluid that surrounds tissues cells

matrix

non-cellular, non-living part of connective tissue

connective tissue differences to epithelial tissue

- never exposed to outside environment
- high vascular (except for cartilage)

wide variety of connective tissue

- bone
- blood
- lymph
- reticular tissue
- fasciae
- adipose tissue

three basic categories of connective tissue

1. connective tissue proper
2. supporting connective tissue
3. fluid connective tissue

connective tissue proper

- tissues that connect and protect
- tendons and ligaments
- adipose tissue

example of supporting connective tissue

cartilage and bone

example of fluid connective tissue

blood and lymph

cells of ctp

- mast cell
- adipocytes
- lymphocyte
- melanocyte
- mesenchymal cell
- fibroblasts
- macrophages

mast cell

trigger local inflammation by releasing their chemicals

example of mast cells

histamines and heparin

adipocytes

fat cells that store energy in lipid molecules

lymphocytes

white blood cells responsible for the "specific defenses"

specific defenses

basis for immunity, vaccines, etc

plasma B cells

make antibodies

mesenchymal cells

stem cells that can divide to make different kinds of ct cells (ex: adipocytes)

fibroblasts

- make ground substance and produce protein fibers
- most common cell type in ctp
- make the matrix

macrophages

large white blood cells that engulf and destroy pathogens, dead tissues, debris, etc

two types of macrophages

- fixed
- free

free macrophages

- go to injured or infected areas
- "ambeoid movement"

3 protein fiber types in ctp

1. collagen fibers
2. reticular fibers
3. elastic fibers

collgen fibers

- give strength to many tissues in body
- make up bones, tendons, and ligaments

reticular fibers

thinner than collagen, with branching structure that forms branched network to support structure of organs

elastic fibers

similar to collagen, but made of protein elastin

characteristics of elastic fibers

- return to original length after stretching
- relatively rare compared to collagen
- common around spine in elastic ligaments

ligamentum nuchae

conects base of skull to C7

two categories of ctp

loose and dense

loose ctp compared to dense ctp

- more ground substance
- fewer fibers
- "packing materials"
- stabilize, fill in spaces, and cushion
- example is adipose tissue

example of dense ctp

tendons and ligaments (tightly packed with collagen and elastic fibers)