Tissues Honors Anatomy Physiology Chapter 4 Human Anatomy

Tissues Honors Anatomy & Physiology Chapter 4 Human Anatomy & Physiology

Tissues & Homeostasis • 4 basic types of tissues in human body contribute to homeostasis by providing diverse functions including • protection • support • communication among cells • resistance to disease • & many more

Definition • a tissue is a group of similar cells that usually have a common embryonic origin & function together to carry out specialized activities

Embryology of Tissues 1. ▫ 2. ▫ 3. ▫ 4. ▫ Epithelial from all 3 layers Connective mesoderm Muscular mesoderm Nervous ectoderm

Tissues • their structure & properties are influenced by factors such as: ▫ nature of the extracellular material surrounding tissue cells ▫ type of connections between cells

Classification of Tissues 1. Epithelial ▫ covers body surfaces & lines hollow organs, cavities, & ducts ▫ forms glands 2. Connective 3. Muscle 4. Nerve

Functions of Epithelial Tissues • protection • absorption • filtration • excretion • sensory reception

Epithelial Tissue • 5 distinguishing characteristics 1. polarity 2. specialized contacts 3. supported by CT (connective tissue) 4. avascular but innervated 5. ability to regenerate

Polarity • apical & basal surfaces ▫ differ in structure & function • most apical surfaces contain microvilli, or cilia • basal surface has thin supporting sheet called basal lamina ▫ selective filter ▫ scaffolding for cells to migrate along

Specialized Contacts • epithelial cells form continuous sheets ▫ not glandular epithelium ▫ lateral cell surfaces see desmosomes & tight jcts (keeps things from diffusing between cells)

Supported by CT • all epithelial sheets rest on CT • reticular lamina: just below basal lamina • basal lamina + reticular lamina = basement membrane

Avascular / Innervated • epithelium contains NO blood vessels ▫ nutrients, O 2 diffuse from underlying CT vessels • has nerve fibers

Regeneration • epithelial cells will reproduce rapidly when neighboring cells damaged or destroyed ▫ as long as necessary nutrients can get to epithelium

Classification of Epithelia • classified according to 2 characteristics: 1. # of layers • single layer = simple • multiple layers = stratified • single layer that looks like multiple = pseudostratified 2. cell shape • squamous • cuboidal • columnar

Squamous Cells • flattened, scalelike • protect

Cuboidal Cells • boxlike, cubes • secretion, absorption

Columnar Cells • tall, column shaped cells • secretion

Simple Epithelium • • 1 layer of cells, often in sheets functions: filtration secretion: production & release of substances (sweat, mucus) • absorption: intake of fluids or other substances

Simple Squamous Epithelium • cells flattened laterally • surface view: tiled floor • cross-section: fried egg • thin, permeable where rapid diffusion important ▫ Lungs ▫ Kidneys

Endothelium • simple squamous epithelium that lines lymphatic and blood vessels and lines the cardiac atria and ventricles • capillaries consist only of 1 endothelial cells thick (site of gas exchange)

Mesothelium • epithelium found in serous membranes ▫ line ventral body cavities ▫ cover organs in ventral cavities

Simple Cuboidal Epithelium • square cells with round, central nuclei in a sheet • secretion • absorption • forms walls of small ducts of glands & kidney tubules

Simple Columnar Epithelium • single layer, tall, closely packed cells • absorption • secretion • line digestive tract where cells have 2 modifications: 1. dense microvilli on apical surface 2. glands that secret mucus (Goblet cells)/intestinal juices

Pseudostratified Columnar Epithelium • cells vary in height • nuclei at variable heights • ciliated or nonciliated • all cells rest on BM (basement membrane) but not all reach free surface ▫ short cells replace tall ones if damaged

Stratified Epithelium • 2 or more cell layers • cells are generated from below • more durable than simple epithelium • protection: major function • type of stratified epithelium determined by cell shape of top layer

Stratified Squamous Epithelium • found in areas subjected to wear and tear ▫ upper layers rubbed away ▫ lower cells replace • top cells are squamous • as cells pushed up further from BM fewer nutrients reach them die lipids from atrophied cells add some water proofing • keratinized/not keratinized ▫ keratin: tough protein

Stratified Squamous Epithelium • upper layers contain keratin: tough, fibrous protein that protects underlying tissues from heat, microbes, chemicals • found: skin • found: lining mouth (buccal mucosa) & esophagus • protect underlying tissues from wear & tear and from invasion by microbes • Keratinized • Nonkeratinized

Stratified Cuboidal Epithelium • rare • found in some ducts of larger glands ▫ mammary glands, some sweat glands • 2 layers of cuboidal cells

Stratified Columnar Epithelium • limited distribution in body ▫ male urethra ▫ some glandular ducts ▫ @junction between 2 other types of epithelial cells

Glandular Epithelium • gland: 1 or more cells that make & secrete a product called a secretion • secretions are aqueous solutions ▫ composition varies by gland

Secretion • active process of gland releasing its product (also called secretion)

2 Classes of Glands 1. Endocrine glands (ductless glands) ▫ internal secretion: cells exocytose extracellular space capillaries target cells prompts some response in cell ▫ hormones: messenger chemicals 2. Exocrine glands (glands with ducts) ▫ external secretion ▫ secrete product onto surfaces or into body cavities

Types of Exocrine Glands Unicellular • Mucous cells & Goblet cells • sprinkled thru GI tract, respiratory tract Multicellular • 2 parts: 1. Duct 2. Secretory cells ▫ surrounded by CT forming fibrous capsule divides it into lobes

Types of Multicellular Exocrine Glands Unicellular Multicellular

Connective Tissue • most abundant & widely distributed of the 4 tissue types • major functions: 1. binding & supporting 2. protecting 3. insulating 4. storing 5. transporting

Classification of CT • CT proper ▫ fat ▫ fibrous tissue • cartilage • bone • blood

Characteristics of CT • common origin ▫ mesenchyme • degrees of vascularity ▫ cartilage: avascular ▫ dense CT poorly vascularized ▫ other types richly vascularized • extracellular matrix ▫ few cells/ lots extracellular matrix

3 Main Elements in CT 1. ground substance 2. fibers 3. cells • 1 + 2 = extracellular matrix • large variation in composition & arrangement of the three large diversity of CTs each adapted to specific function

Ground Substance • fills space between cells • contains fibers • function: molecular sieve • consists of ▫ water ▫ interstitial fluid ▫ cell adhesion proteins (glue)

CT Fibers • provide support • secreted by fibrocytes • 3 types: 1. collagen 2. elastic fibers 3. reticular fibers

Collagen Fibers • made of cross-linked protein collagen ▫ #1 protein in body ▫ very strong, high tensile strength

Elastic Fibers • long, thin, branching fibers • made of protein: elastin • can be stretched return to original shape • function: provide elasticity to tissues • found in: cartilage, skin, lungs, blood vessel walls

Reticular Fibers • form delicate networks that surround small blood vessels& support soft tissue organs (liver, spleen) • made of collagen derived protein • also found in BM of epithelium, around capillaries

CT Cells • each class of CT has resident cell type: ▫ immature form –blast ▫ mature form - cyte

Loose CT • 3 types: 1. Areolar 2. Adipose 3. Reticular

Areolar CT • Functions: ▫ support & bind other tissues ▫ hold body fluids (reservoir of water & salts) ▫ store nutrients • Cells: all CT cells • Features: loose arrangement of fibers • Found: subcutaneous tissue

Adipose Tissue • Functions: store triglycerides, insulation, protection • Cells: adipocytes • Features: scant matrix, closely packed cells, rich blood supply • Found: ass’c w/areolar CT, around heart, kidneys, lymph nodes

Adipose Tissue • 2 types: 1. White: most adipose tissue 2. Brown: abundant mitochondria ▫ use fat to generate heat (less ATP, more heat) ▫ found on back of newborns: unable to shiver if chilled

Reticular Connective Tissue • Function: reticular fibers form internal framework = stroma • Cells: fibroblasts = reticulocytes • Features: only fibers are reticular • Found: lymph nodes, spleen, bone marrow

Dense CT • 3 types: 1. Dense Regular 2. Dense Irregular 3. Elastic

Dense Regular CT • Functions: resistance to tension • Cells: fibroblasts • Features: closely packed, parallel collagen fibers (parallel to direction of pull); appears white, flexible • Found: tendons (muscle to bone) & most ligaments (bone to bone)

Cartilage • Function: withstands tension & compression • Cells: chondroblasts (lay down cartilage), chondrocytes found in lacunae • Features: qualities intermediate between dense CT and bone, no nerve or blood supply, surrounded by perichondrium • Found: ends of long bones, see next slide

Types of Cartilage 1. Hyaline 2. Elastic 3. Fibrocartilage

Hyaline Cartilage • Function: provides flexibility & support • Cells: chondrocytes in lacunae • Features: matrix appears glassy, most abundant type of cartilage, • Found: embryonic skeleton, tips of nose, ends of long bones, connects ribs, to sternum, trachea, epiphyseal plates

Elastic Cartilage • Function: maintains shape, strength and elasticity • Cells: chondrocytes in lacunae • Features: very flexible • Found: pinna, epiglottis

Bone: Osseous Tissue • Function: support and protect, cavities allow storage of fat and production of blood cells • Cells: osteoblasts, osteocytes, osteoclasts • Features: hard but some flexibility, more collagen than cartilage + inorganic calcium salts • Found: skeletal system

Bone • 2 types: 1. Compact Bone 2. Spongy Bone

Compact Bone • basic unit of compact bone is the osteon (haversian system) • has 4 parts: 1. Lamellae ▫ ▫ concentric rings of extracellular material & collagen make bone hard & strong 2. Lacunae 3. Canaliculi 4. Central (haversian) canal)

Spongy Bone • lacks osteons • found only inside compact bone • consists of columns of bone called trabeculae ▫ spaces between trabeculae filled with red bone marrow

Blood • liquid CT made up of: • Plasma ▫ liquid portion of blood (yellow) ▫ water, dissolved nutrients, wastes, plasma proteins, hormones, gases, ions • RBCs: transport O 2 • WBCs: phagocytes, immune response, allergic reactions • Platelets: cell particles involved in blood clotting

Muscle Tissue • Function: movement, maintain posture, generate heat • Cells: muscle fibers containing actin and myosin • Features: contraction & relaxation • Found: skeletal system, walls of vessels and hollow organs, heart

Smooth Muscle • Function: movement • Cells: 1 central nucleus, fusiform cells • Features: involuntary & not striated, innervated by ANS, • Found: walls of vessels & hollow organs, between hair follicles and dermis

Cardiac Muscle • Function: propel blood thru body • Cells: branching with gap jcts = intercalated discs • Features: striated, involuntary (ANS) • Found: only in wall of heart

Skeletal Muscle • Function: move bones • Cells: multinucleated (peripherally located) muscle fibers • Features: striated and voluntary • Found: attached to bones or skin

Nervous Tissue • Function: regulate and control body functions • Cells: neurons, neuroglial cells • Features: neurons can generate and/or respond to action potentials • Found: nervous system

Membranes • are flat sheets of pliable tissue that cover or line a part of the body • 2 types: 1. epithelial membrane: ▫ ▫ epithelial layer + underlying CT types: mucous membrane, serous membrane, cutaneous membrane (skin) 2. synovial membrane: ▫ ▫ + CT but - epithelium line joints

Mucosae (Mucous Membranes) • Function: absorption and secretion • Cells: stratified squamous epithelium or simple columnar epithelium, lie over CT layer = lamina propria • Features: moist, most secrete mucus • Found: line all body cavities that open to outside body

Serosa (Serous Membranes) • Function: lubrication • Cells: simple squamous epithelium (called mesothelium) on areolar CT • Features: moist, squamous cells secrete thin watery serous fluid, serosa named according to organ: pleura, pericardium, peritoneum • Found: closed ventral cavities

Tissue Repair • 3 phases: 1. Inflammation 2. Organization 3. Regeneration/Fibrosis

Inflammation • nonspecific reaction • injury causes tissue cells, macrophages, mast cells inflammatory chemicals capillaries dilate & become more permeable neutrophils, monocytes & plasma fluid (clotting factors, abys) enter injured area form clot stops bleeding, holds wound together, isolating injured area giving some protection to infection scab forms

Inflammation • Characterized by area of: • redness (rubor) • swelling • +/- pain (dolor) • warmth

Organization Phase of Tissue Repair • begins during inflammatory pahse • blood clot replaced by granulation tissue: a friable, delicate tissue ▫ capillaries ▫ fibroblasts collagen, growth factors when phase complete become inactive or apoptosis ▫ macrophages phagocytize injured cells/cell debris, clot

Organization Phase of Tissue Repair

Regeneration & Fibrosis Phase • fibrous tissue beneath scab matures epithelium regenerate until it resembles surrounding skin • +/- scar tissue

Injury Below Skin • skin surface not breached • usually involves infection (pimple, sore throat) ▫ minor : heals by regeneration only ▫ more serious clot formation possibly scarring

Scar Tissue • permanent fibrous patch • if wound was extensive replaced only with scar tissue does not replace function of normal tissue • adhesions: scar tissue that forms around irritated organs in abdominopelvic cavity or w/in hollow organs

Healing in Different Tissues • heal well: epithelium, areolar CT, dense irregular CT, bone, blood forming tissue • moderate capacity to heal: smooth muscle, dense regular CT • poor healing: skeletal muscle, cartilage • NO healing: cardiac muscle, nerve tissue

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