Chapter 4 Histology

Histology- the study of the normal structure of tissues

Tissue- a group of structurally and functionallyrelated cells and their external environment that together perform common functions

extracellular matrix(ECM)- surrounds the cell/ ground susubstance and protein fibers

Functions Extracellular- provides the tissue with the strength to resist tensile and compressive forces/ direct cells to their proper places/ regulates the development, and survival of cells/ holding calls in proper position 

extracellular fluid(ECF)- apart of ECM

epithelial tissue- sheet of cells that are tightly packed together with little visible ECM/ covers and lines all body surfaces and cavities/ forms glands

five functions of epithelial tissue

protection- produces hard protein keratin

immune defenses- immune cells are scattered throughout epithrlial tissues

secretion- allows glands to secrete hormones

transport into other tissuesselectively permeable barriers that allow certain substances to pass by passive or active transport

sensation- supplied with nerves that detect changes in internal and eexternal environment

connective tissue- cellular velcro that connects all other tissues in the body to one another/ ECM is the most prominent feature, and cells are scattered throughout it/ bind, support, protect, and allow the transport of substances through the body

Muscle tissue- composed of cells that can contract and generate force, 

nervous tissue- generate, send, and receive messages, and other cells that help with this/ 

Ground Substance- contains the extracellular fluid

cell junctions- connections of neighboring cells in a tissue linked to one another by integral proteins

tight junctions- similar to a zipper/ intrgral locking proteins in adjacent plasma membranes prevents passsage of macromolecules/ some are leaky 

desmosomes- junctions composed og integral linker proteins in ajacent plasma membranes

gap juctions- cmall pores made of protein channels in agjacent plasma membranes/ pass 

cells can be identified bc the DNA in their nuclei stain dark purple

ecm has grounf substance that looks clear or light colored 

component of epithelia

apical surface- top of the tissue

basal surface -bottom of tissue 

basement membrane- between the two tissues

classification of epithelia:layer and shapes

simple epithelia- single layer of cells

stratified epithelia- more than one layer of cells

pseudostratified eoithelia0 single layer of cells that appear to be multilayered

squamous cells- flattened cells

cuboidal cells- short cells/ square

columnre cell- tall and elongated cell

exocrine glands- local actions only

three tyoes of exocrine secretion

merocrine- breaks through the wall of cell then releases

holocrine- cell ruptures and secretes 

apocrine- pinched off

endocrine glands- secretes directly into blood stream

goblet cell- secretes mocus in the digestive and respiratory

four connective tissue functions

connecting and binding

support

protection

transport

five cells of connective tissue proper

fibroblasts- produce protien fibers

adipocytes- Fat cells with single large inclusion that contains lipids with organelles pushed to the perimeter

mast cells- cells of the immune system with cytosolic inclusions containing inflammatory mediators such as histamine 

phagocytes- immune cells that phagocytize foreign substances, microorganisms, and dead and damaged cells

othe immune cells( t and b cells)- other cells of the immune system can move in and out of connective tissues dependikng on the needs of the body

loose connective tissue- contains gtound substance with protein fibers, fiberblast 

dense irregular connective tissue- protein fibers with mostly collagen fibers/ found in the dermdermis and arounf organs

dense regular connective tissue- contains think collagen fibers arranged in parallelbundles/ found in tendones and ligaments

dense regular elastic connective tissue- elastic tissue/ found in large blood vessles and ligaments 

recticular connective tissue- used to trap foregin cells/ numeroue reticular fibers produced by surrounding fibroblasts

adipose tissues connective tissue- fat tissue consisting of adipocytes surrounding fibroblasts and ecm

most adipose tissue is white adipose

brown adipose more common in children 

cartilage- cartilage is avascular/ tough fleaible tissue that absorbs shock; resistant to tension, compression, and shearing forces

perichondrium is a layer tha covers cartilage and supplies nourishment/ made out of dense irregular connective tisssue

two cell types for cartilage 

chondroblasts- immmature cartilage cells

chondrocytes- mature cartilage cells; housed in cavities called lacunae

hyaline cartilage- most common covers ends of bones, rib attachment sites to sternum, and nose and respiratory tract; makes up most of fetal skeleton

fibrocartilage- ecm is filled bundles of collagen and some elastic fibers made by fibroblasts; found in fibrous joints including the intervertenral discsand other articular discs that improve the fit of 2 bones: lacks a perichondrium

elastic cartilage- ecm folled with elastic fibewrs: found in external ear pinna and parts of framework of larynx: tissue vibrates and assists in detection of sound on the air and production of sound by larynx

bone functions- supports, protects, provides attachment sites for muscle, stores calcium, houses bone marrow which produces almolst all components of blood

bone ECM- organic portion= 35% is collagen, fibers, and osteoid/ inorganic portion= 65% calcium Phosphate crystals

bone cells 

osteoblasts- immature cells

osteocytes- mature osteoblasts 

osteoclasts- breajs down bone cells

bone remmodeling- bone deposition and bone resorption are constantly occurring in healthy bone, depending on type of stress placed

blood- main function is to transport

ECM is plasma; contains water, dissolved solutes, and globular protein

cells of blood

erythocytes (RBC)- O2 carries

leukocytes (WBC)- Immunity

Platelets- blood clotting

muscle cells (Myocytes)- excitable cells that respond to electrical or chemical sstimulation

myofilaments- are a bunch of proteins bundled in the cytoplasm/ the proteins are myosin and actin

striated muscle cells- myofilaments are organized into regions that produce dark and light areas called bands or striations

smooth muscle cells- myofilaments are in irregular bundles scattered in the cytoplasm so no striations are visable

hypertrophy- growth of muscles 

atrophy- break down of muscle 

skeletal muscle- found attached to the skeleton to produce body movement; controlled by the nervous system/ voluntary

formed by the fusion of embryonic myoblasts resulting in large, multinucleate cells

cardiac muscle- found only in the heart/ involuntary contraction/ shorter with branches and a single nucleus/ intercalated discs, which contain gap junctions and tight junctions, are found between cells and permit heart muscle to contract as a unit

smooth muscle- found in the walls of hallow organs/ walls of blood vessels, eyes, skin, glands/ involuntary contractions/ cells are flat, with single nucleus/ gap junctions in the plasma membrane connect cells to other smooth muscle cells

nervous tissue- makes up majority of the brain, spinal cord, and nerves/ ECM is different has less protein fibers with unique proteoglycans

nervous cells

neurons- generate, conduct, and receive nerve impulses

neurons are amitotic

structure of a nerve

cell body- large center with nucleus and organelles

axon- moves impulse to target cell

dendrites- arms that receive messages

neuroglial cells- supportive cells that anchor neurons and blood vessels in place/ monitor the composition of the ECF/ speeds up nerve impulse transmission/ circulate fluid around the brain and spinal cord

neuroglial cells can divied by mitosis

membrane- thin sheet of one or more tissues that lines a body surface of cavity 

four types of membranes

true membranes - fit the structure and functional definitions of a membrane; do not open to outside of body

serous membranes- lines pleural, pericardial, and peritoneal body cavities

consist of a layer of simple squamous epithelial tissue called MESOTHELIUM its basement membrane, and loose connective tissue

Mesothelial cells produce serous fluid, which lubricates organs to prevent friction

synovial membranes- line cavities surrounding freely movable joints, including the hip, knee, elbow, and shoulder

made of two connective tissue- inner layer fibroblasts called synoviocytes they secrete synovial fluid which lubricates the joint/ external layer is a mixture of loose and dense irregular connective tissue

membrane like structures

mucous membranes- lines all body passages as part of walls of hollow organs that open to the outside of body

consists of a layer of epithelium, its basement  membrane, a layer of loose connective tissue called laminate propria and sometimes smooth muscle/ include glands with goblet cells that secrete mucus

cutaneous membrane- refers to the skin which is largest organ of the body

tissue repair- process of wound healing; occurs differently in different tissues and is dependent on tissues ability to regenerate

two processes of healing

regeneration- damaged or dead cells are replaced with cells of the same type

fibrosis- fibroblasts divide by mitosis and produce collagen to fill in defect left by injury; results in scar tissue, which is dense irregular connective tissue

regeneration or fibrosis occurring in tissue largely determined by ability of tissue to undergo mitosis

tissue types and their mode of healing

epithelial tissue- typically undergo regeneration

connective tissue- most heal by regeneration

cartilage is an exception and often heals by fibrosis

smooth muscle tissue- usually regenerates/ undergo mitosis

cardiac and skeletal muscle generally heal by fibrosis

cardiac and skeletal muscle cell size and complexity prevents mitosis

satellite cells in skeletal muscle tissue can divide and become skeletal muscle cells which provides a limited degree of regeneration

neurons of nervous tissue generally do not regenerate

nutrition and blood supply are also important determinants of tissye repair

nutrition- collagen is neede in tissue repair, so protein intake and vitamin c must be considered

blood supply- adequate blood flow to injured areas is also important