A &P Chapter 4

primary tissue types

1. epithelial tissues

2. connective tissues

3. muscle tissues

4. nervous tissues

Defined by kind and number of cells, amount and composition of ECM and specific functions

epithelial tissues

• tightly packed sheets of cells with no visible ECM

• cover and line all body surfaces and cavities

• specialized tissues form glands that manufacture secretions (sweat, saliva, or chemical messengers, like hormones)

connective tissues

• connect all other tissues to one another like Velcro

• ECM is a prominent feature for most connective tissue types

• cells scattered throughout

• bind, support, protect, and allow for transportation of substances

muscle tissues

• capable of generating force by contracting

• little ECM between cells

nervous tissues

• capable of generating, sending, and receiving messages

• cells that support this activity within unique ECM

Extracellular matrix

substances in liquid, thick gel, or solid form that surround cells of tissue

• ground substance and protein fibers

ECM functions

• provides tissue with strength to resist tensile and compressive forces

• direct cells to proper positions within tissue and holds those cells in place

• regulates development, mitotic activity, and survival of cells in a tissue

• holds cells in their proper positions

ground substance

• most of ECM

• extracellular fluid/interstitial fluid with water, nutrients, ions, and macromolecules

ground substance macromolecules

GAGs, proteoglycans, CAMs

Glycosaminoglycans

• GAGs

• polysaccharide chains

• chondroitin (small) and hyaluronic acid (enormous)

• negative charges of sugars attract positively charged ions in ECF

• these ions create a concentration gradient within ECF and draw water out of cells and blood vessels via osmosis, which trap water in ECM and help it resist compression → Gradients Core Principle

Proteoglycans

• GAGs bound to protein core

• thousands of these bind to a very long GAG (ex hyaluronic acid) and forms huge ______ aggregates which make ECM firmer, more solid, and resistant to compression

• aggregates form barrier to diffusion of substances through ECM and protect underlying tissue from invading microorganisms

Cell-adhesion molecules

• different types of glycoproteins

• adhere cells to cells

• adhere cells to surroundings

• hold everything in place within ECM like glue

• bind to cell surface proteins, protein fibers, and proteoglycans

• maintain normal tissue architecture

protein fibers

• embedded within ground substance

• long molecules composed of multiple fibrous subunits with ropelike structure

• enormous tensile strength

• three types: collagen, elastic, and reticular

collagen fibers

• make up 20-25% of all proteins in body

• composed of multiple repeating subunits

• form white fibrous protein

• restraint to tension and pressure

elastic fibers

• surrounded by glycoproteins

• extensibility allows fibers to stretch without breaking and return to their resting length

reticular fibers

• thin, short collagen fibers

• form meshwork or scaffold that supports cells and ground substance of many tissues

• form weblike structure in organs such as the spleen that helps trap foreign cells

cell junctions

• another way cells bind to one another

• neighboring cell’s plasma membranes are linked by integral proteins

• 3 major types: tight, desmosomes, and gap

tight/occluding junctions

• hold cells closely together

• space between is impermeable to movement of macromolecules

• integral proteins of adjacent cell’s plasma membranes are locked together and form a seal around apical perimeter of cell like a zipper

• seal may not be complete, allowing leakage for some tissues

• Ex: between cells in blood vessels (prevent blood cells from exiting vessels)

desmosomes

• linking integral proteins

• allows for materials in ECF to pass through space between cells (more like a button)

• increase strength of tissue by holding cells together → mechanical stress is more evenly distributed

• integral “linker” proteins are attached to intermediate filaments of cytoskeleton for structural reinforcement

• located in tissues that are subjected to a great deal of mechanical stress (ex: epithelia of skin)

gap junctions

• small pores formed by protein channels between adjacent cells

• allow small substances to flow freely between each cell’s cytoplasm

• located in between cells that communicate with electrical signals

• illustrate cell to cell communication core principle

epithelia tissues

• on every external and internal body surface

• barrier between body and external environment

• line organs and fluid filled cavities

epithelial tissue functions

• protection - shield underlying tissues from mechanical and thermal injury

• immune defense - form physical barrier to prevent invasion by microorganisms; specialized immunity cells are scattered throughout tissue

• secretion - form glands that produce hormones and oils

• transport into other tissues - selectively permeable membranes

• sensation - rich nerve supply; detect changes in internal and external environments

basement membrane components

basal lamina and reticular lamina

• two layers glue epithelia tissue to underlying connective tissue, anchor underlying blood vessels in place, and provide barrier between epithelia and underlying tissues

basement membrane

beneath cells; where ECM is found

basal lamina

• ECM is synthesized by epithelial cells

• consist of collagen fibers and ground substances

reticular lamina

• synthesized by underlying connective tissue

• consists of ____ fibers and ground substance

simple epithelia

single cell layer

stratified epithelia

• more than one cell layer

• best as productive barriers where subjected to high degrees of mechanical stress

epithelia classification

classified by number of cell layers and shape of cells in those layers

cuboidal cells

short

squamous cells

flattened

columnar cells

tall and elongated

simple epithelia function

• adapted for transportation of substances between different tissues

• some have microvilli for increased surface area

• some have cilia (move through hollow organs)

• structure-function core principle

types of simple epithelia

simple squamous, simple cuboidal, simple columnar, pseudostratified columnar epithelium

simple squamous epithelium

simple squamous epithelium function

• adapted for rapid diffusion of substances (oxygen, carbon dioxide, fluids, and ions)

• located in air sacs of the lung (parietal pleura), specific segments of kidney tubules, and lining of blood vessels, lymphatic vessels and alveoli

simple cuboidal epithelium

simple cuboidal epithelium function

• large central nucleus

• thin enough for rapid substance diffusion

• located in segments of renal tubules, respiratory passages, the ducts of many glands (ex: salivary; mammary), and thyroid gland

simple columnar epithelium

simple columnar epithelium function

• nuclei in basal portion of cell

• The apical plasma membranes of these cells are often folded into microvilli, which increases their surface area for absorption → mostly in small intestine

• may also contain cilia on apical plasma membrane → mostly for uterine tubes and segments of respiratory tract

• lines digestive tract, uterine tubes, gall bladder, certain kidney tubules

pseudostratified columnar epithelium

pseudostratified columnar epithelium function

• nuclei are at varied heights which gives a layer look

• only one cell layer thick with basal plasma membranes firmly in contact with basement membrane

• ciliated

• line upper respiratory tract, a part of the male urethra, and nasal cavity

types of transport across simple epithelia

paracellular transportation and transcellular transportation

paracellular transportation

• substances “leak” between cells in epithelial membrane

• limited due to tight junctions that makes spaces between cells nearly impermeable

• passes through narrow space between cells

transcellular transportation

• think through

• substance enters cell by crossing plasma membrane, diffuses across cytosol, and exits through plasma membrane at opposite side

stratified epithelium types

keratinized stratified squamous; nonkeratinized stratified squamous; stratified cuboidal; stratified columnar; transitional epithelium

keratinized stratified squamous epithelium

• apical cellular layers are dead + lack nuclei

• filled with keratin (a protein) which make tissues tough and resistant to friction

• well adapted for outer layers of skin

nonkeratinized stratified squamous epithelium

• apical cellular layers retain nuclei and are still alive

• located in regions subjected to mechanical stress where surface must remain moist

• located in mouth, throat esophagus, and vagina

stratified cuboidal epithelium

stratified cuboidal epithelium function

• rare in humans

• two cell layers

• lines ducts of sweat glands, mammary glands, and the pancreas

• lines developing ovarian follicles and seminiferous tubules

stratified columnar epithelium

stratified columnar epithelium function

• rare in humans

• few layers - apical layer is columnar and basal layer is cuboidal

• located in male urethra, cornea of eye, ductus deferens and ducts of certain glands (ex: salivary glands)

transitional epithelium

transitional epithelium function

• only in urinary system

• lines interior of kidneys, ureters, urinary bladder, and urethra

• cuboidal basal layers and apical cell layers are dome-shaped when the tissue is relaxed

• apical cells can flatten which allows tissues to stretch → think about bladder expanding to hold pee

gland

• arises from epithelial tissue that migrated into deeper connective tissue instead of remaining at surface

• synthesizes and secretes product from designated secretory cells

• classified by shape or how products are released

• mechanisms: endocrine/exocrine

endocrine glands

• secretes products, usually hormones, directly into blood stream without use of ducts which allows product to have large effects on distant cells

• the communication between cells in distant areas of body → cell-cell communication core principle

exocrine glands

• release products onto apical surfaces of epithelium (external surface of body) or lining hollow organs that open to outside of body

• products that are secreted from gland through epithelial-lined duct only have local effects in gland-vicinity

• glands vary in complexity

• 3 possible configurations: acinar, tubuloacinar, and tubular

goblet cells

• most common unicellular exocrine gland

• in digestive and respiratory tracts

• secrete mucus that protects underlying epithelium

exocrine gland classification

• multicellular

• classified according to structure of ducts and shape of clusters of secretory cells

• simple glands - don’t branch

• compound - do branch

simple tubular

long and straight

simple acinar

spherical

tubuloacinar

both tubular and acinar portions

compound acinar

compound tubuloacinar

merocrine

• used by majority of exocrine glands (including salivary and sweat glands0

• products packages in secretory vesicles for release by exocytosis into ducts

holocrine

• used by sebaceous glands in skin to secrete sebum

• secretory cells accumulate product in cytosol and only release product when cell ruptures and dies

• cells replaced by mitosis at gland base

apocrine

• rare type of secretion

• portions of cytoplasm are pinched off when product is being secreted

• observed during liquid lipid droplet secretion in lactating mammary glands of many mammal species

connective tissue functions

• connecting and binding - anchor tissues layers in organs and link organs together

• support - bone and cartilage support weight of body

• protection - bone tissue protects internal organs; cartilage and fat provide shock absorption; components of immune system are throughout tissues

• transport - blood is fluid ____ tissue; main transport medium in body

connective tissue components

• cells (surrounded by protein fibers and embedded in ground tissue) and ECM

connective tissue proper

• widely distributed in body

• connect tissues and organs to one another

• components of internal architecture of some organs

cells of connective tissue proper

fibroblasts; adipocytes; mast cells; phagocytes; other immune system cells

fibroblasts function

• most common resident cell

• mature cells with properties of immature blast cells

• make protein fibers and ground substance (components of ECM)

• continually produce collagen proteins

fibroblasts

adipocytes

adipocytes function

• fat cells

• in many different connective tissues

• cytoplasm filled with single large lipid inclusion (triglycerides) - takes up most of cell so nucleus is pushed to the side