Chapter 4

Tissue Level of Organization

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. tissue = a group of identical or similar cells working together to perform a function • 4 categories • components – ALL – epithelia tissues have: • 1 ; epithelial = adjective – cells • note grammar – extracellular matrix – connective tissues = ECM • ground substance – nervous tissue • fibers – muscle tissues TISSUE TYPES tissue = a group of identical or similar cells working together performing specific functions epithelia [epithelium; epithelial] first connective tissues … next nervous tissue … when we get to NS muscle tissue … when we get to muscles EPITHELIUM / EPITHELIA = EPITHELIAL TISSUE

• mostly cellular: closely packed • tight adherence; junctions • very little ECM • polar • form continuous sheets; boundary layers – line body cavities & hollow organs – surface most organs & body EPITHELIUM / EPITHELIA = EPITHELIAL TISSUE • overlie & adhere to CT – basement membrane • have nerve supply • avascular • high capacity for renewal since ordinarily subjected to wear & tear • derive from all 3 germ layers • diverse functions – most glands are epithelial or derivative EPITHELIUM / EPITHELIA = EPITHELIAL TISSUE • polar: apical, basal aspects • junctions: – tight junctions – intermediate/adhering junction -- terminal web – – tonofilaments – –

• basement membrane = + reticular lamina Functions of Epithelial Tissue

• physical protection/ defense against (e.g.) – dehydration – abrasion – physical, chemical, and biological agents • selective permeability: regulate passage of molecules in or out of certain regions of the body • secretion: secrete substances for use in the body e.g. – hormone – – for elimination from the body (e.g., sweat) = excretion • sensation: possess nerve endings that can detect light, taste, sound, smell, and hearing JUNCTIONS

• tight junctions = zonula occludens • intermediate/adhering junction = zonula adherens • desmosome = macula adherens

• zonula: forms a continuous strip, a stripe around the cell • macula: a spot • occludens: to occlude is to stop, close up, or obstruct (e.g. an opening) • adherens: to adhere is to stick together Figure 4.1

Overview – epithelia in general JUNCTIONS tight junctions = zonula occludens • “gatekeeper” prevent material from passing between cells • force material to go through cells – selective permeability intermediate/adhering junction = zonula adherens • microfilaments act like a purse string to stabilize the apical surface of the epithelial cell desmosome = macula adherens • ~ button, snap instead of ~ zipper or tape • @ points of mechanical stress • thickened protein plaque on apposed membranes • fine network of proteins spanning the intercellular space • intermediate filaments attach to cytoplasmic side of plaques • provide support and stability : between single cell & basement membrane gap junction: span the intercellular space between neighboring cells • connexon = group of membrane proteins that forms a pore – fluid filled pore connects the of the two cells • allow adjacent cells to communicate with each other – by the flow of ions and small molecules Table 4.2 Epithelia are categorized by ** number of cell layers ** shape of cells in apical layer Epithelia are categorized by ** number of cell layers ** shape of cells in apical layer number of layers: cell shape • simple epithelium = one cell • squamous layer thick • cuboidal • stratified epithelium = more • columnar than one cell layer thick

and then, there are pseudostratified epithelium and transitional epithelium, breaking the pattern  Types of Epithelia

Figure 4.3 Table 4.3

simple squamous epithelium

and

simple cuboidal epithelium Figure 4.2 simple and stratified squamous epithelia Table 4.3 continued

ciliated and non-ciliated

simple columnar epithelia

goblet cells Table 4.4 keratinized and non-keratinized

stratified squamous epithelia Figure 4.3 goblet cells are unicellular glands Table 4.5 and then, there are

pseudostratified epithelium

and transitional epithelium,

breaking the pattern  Table 4.4 continued stratified cuboidal

and stratified columnar epithelia Glands and Secretory Types

What is the difference between secretion and excretion?

What is inside the body and what is outside? Figure 4.4 acinar glands Figure 4.5 simple and complex gland shapes Figure 4.6

Modes of Secretion

(will revisit: mostly in skin & digestive system) Glands and Secretory Types gland structural categorization • complexity of the duct • shape of the secretory portion – ducts type distinguishes simple from compound glands – secretory portion can be tubular, acinar or tubuloacinar gland secretion types – serous glands produce watery fluids (such as sweat) – mucous glands secrete mucin – mixed glands produce a mixture of watery and mucoid secretions (e.g. salivary glands - oral cavity) Connective Tissues

• mostly ECM • few cells – separated from one another • categories based on ECM characteristics – ECM ranges from fluid - fibrous - flexible -rigid • not found on free surfaces • found under epithelia &/or between cells, tissues, organs – connective tissue ~ “glue” (not always) • has nerve supply (except cartilage, blood) • highly vascular – (except cartilage; tendons are slightly vascularized) • mesodermal origin (all) Connective Tissues - Development MESODERM: • embryonic mesoderm – epithelial layers that follow • ectoderm → parietal/somatic membranes and associated structures • endoderm → visceral/splanchnic membranes and associated structures – mesenchyme

• mucous connective tissue – in umbilical cord – → stem cells in embryo → → → adult Connective Tissues

• all CTs have cells, fibers and ground substance – *** all tissues do! *** • categories based on ECM – fibrous CTs – cartilagenous CTs – bone – blood [discuss in cardiovascular system section] • ECM is produced by CT cells except for blood Connective Tissues – Functions (include)

• physical protection • support and structural framework • binding of structures • storage • transport • immune protection Connective Tissues ECM

FIBERS + GROUND SUBSTANCE

• hyaluronic acid • collagenous fibers – viscous fluid; lubricates e.g. in joint, – type I collagen binds cells together, major component of viscous humor => eyeball shape; – up to ~ 25% protein in body • chondroitin sulfate • reticular fibers – jellylike for support & adhesiveness -- – collagen (other e.g. in bone & cartilage; types) + glycoprotein • dermatan sulfate, • elastic fibers • keratan sulfate, • etc …… specialized funx. – elastin Figure 4.8 Connective Tissues Categories: “CT proper” & supporting & fluid CTs Fibrous CT = “CT Proper” categories dense – loose by fiber size Areolar CT “film”

fibroblast or fibrocyte? that is the question **

Figure 4.7 Areolar CT “film” Table 4.7 Cells of CT proper resident = fixed vs wandering Table 4.9 Loose CTs:

areolar CT

adipose tissue reticular tissue adipose tissue

loose CTs: Table 4.6 Embryonic CTs:

mesenchyme

“mucous CT” Table 4.10 Dense CTs:

dense regular fibrous CT (DRFCT)

dense irregular fibrous CT (DIFCT) dense CTs: elastic CT

DIFCT Figure 4.8 Connective Tissues Categories: “CT proper” & supporting & fluid CTs Cartilage and Bone: supporting CTs

• solid ECM • fibers are not the predominant feature – in some cartilage tissues, fibers are evident – in bone, fibers are evident in “wet prep” but not in dry preparations • cells in lacuna(e) • nutrient and waste product diffusion problems must be solved CARTILAGE • chondrocyte chondroblast – XXXX-cyte = “mature” cell – XXXX-blast = immature cell that can only either • → more XXXXblasts, -→ XXXXcytes …. or die • lacuana(e) • perichondrium (except fibrocartilage) • matrix

hyaline cartilage: “basic form” • “glassy” matrix; chondrocytes in lacunae • most common type of cartilage, but also the weakest • smooths joint surfaces, model for bone growth • example: articular cartilage of long bones Table 4.11 Cartilage:

hyaline cartilage

fibrocartilage ~ hyaline cartilage + thick, ~ parallel collagen fibers Table 4.11 continued all cartilage:

• chondrocyte chondroblast • lacuana(e) • perichondrium (except fibrocartilage) • matrix

• avascular

elastic cartilage – • ~hyaline cartilage + elastic fibers Table 4.12 BONE = osseous tissue -- more to come

• Haversian system = osteon – Haversian = central canal • blood & lymphatic vessels, nerves – osteocytes in lacuna(e) – canaliculi • Lamella(e) – concentric – interstitial • Volkman’s = perforating canal Table 4.13 BLOOD -- more to come

note – the only CT where the ECM is not mostly made by the resident cells Page 11301 Gangrene … necrosis due to diminished blood supply Table 4.14 muscle tissue

striated muscle tissues:

skeletal muscle

cardiac muscle Table 4.14 continued smooth muscle

(non-straited) Table 4.15

nervous tissue

this is a neuron nervous tissue these are neurons Tissue Changes and Death tissues can undergo change in form, size or number during the aging process, or due to damage, injury, disease:

• metaplasia – epithelia lining the respiratory airways of people who smoke change from pseudostratified ciliated to stratified squamous epithelium • hypertrophy – increase in the size of existing cells • hyperplasia – increase in the number of cells in a tissue • neoplasia – out of control growth which forms a tumor • atrophy – shrinkage of tissue either by cell size or cell number