Chapter 4 The Tissue Level of Organization The original lecture presentation by Lee Ann Frederick (University of Texas at Arlington) has been extensively modified for use in MCB 244 & 246 by Drs. Kwast & Brown, University of Illinois at Champaign-Urbana (2016–2017)

© 2015 Pearson Education, Inc.

Chapter 4: Learning Objectives • Understand the fundamental characteristics, classifications, structure/functions and locations of the 4 basic types of tissue and membranes:

1. 2. 3. 4.

Epithelial tissue (8 types + glands) Connective tissue (3 + many cell types) Muscle tissue (3 types) Neural or nervous tissue

Membranes = epithelial + connective tissue (4 types) 2

4-1 An Introduction to Tissues • Tissues • Collection of specialized cells (and their products) that perform limited number of specific functions • Have discrete structural and functional properties • Tissues in combination form organs (e.g., heart, liver) • Organs can be grouped into 11 organ systems • Histology is the study of tissues While there are some 200 types of cells, there are only four types of tissues in the body. 3

4-1 Four Types of Tissue 1. Epithelial tissue: “covering ” • Lines internal passages & covers exposed surfaces • Specialized for absorption and secretion • Forms glands 2. Connective tissue: “support ” • Fills internal spaces • Supports other tissues • Transports materials • Stores energy

3. Muscle tissue: “movement ” • Specialized for contraction • Skeletal muscle, heart muscle, and smooth muscle lining the walls of hollow organs 4. Neural tissue: “control ” • Carries electrical signals from one part of the body to another, excitable membranes

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4-1 Three Primary Germ Layers • Embryonic germ layers give rise to all four tissue types in adults: • Ectoderm (outer): epithelial (epidermis) & nervous • Mesoderm (middle): muscle, connective, epithelial (endothelium - lines blood & lymph vessels + mesothelium - lines pleural, pericardial & peritoneum cavities) • Endoderm (inner): epithelial (mucosa - lines GI & respiratory tracts)

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4-2 Epithelial Tissue • 2 Categories: • Epithelia - layers of cells covering internal or external surfaces • Glands - structures that produce fluid secretions

• Characteristics of Epithelia • Cellularity – closely packed cell junctions w/little extracellular material between adjacent cells; tight junctions between cells • Polarity – apical (exposed) and basal (attached) ends, separate functions • Attachment – bound to basement membrane (basal lamina) • Avascularity – lack blood vessels (no room) so obtain nutrients from underlying connective tissue or through apical membrane • Regeneration – high turnover; damaged or lost cells continually replaced by epithelial stem cells

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4-2 Epithelial Tissue Morphology & Specialization 1. Apical Surface: exposed to environment, may have: • Microvilli: absorption or secretion • Cilia: fluid movement

2. Basolateral Surfaces: attachment to neighboring cells via intercellular connections; also attachment to basement membrane

• Specializations of Epithelial Cells 1. Move fluids over the epithelium (protection)

Figure 4-1 The Polarity of Epithelial Cells

2. Move fluids through the epithelium (permeability) 3. Produce secretions (protection and messengers)

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4-2 Epithelial Tissue Functions • Functions of Epithelial Tissue 1. Provide physical protection of exposed and internal surfaces (abrasion, dehydration, infection, etc.) 2. Control permeability – selective absorption or secretion (regulated) 3. Provide sensation – large sensory nerve supply (e.g., touch); includes neuroepithelium for specific modalities (taste, smell, sight, equilibrium & hearing) 4. Produce specialized secretions (glandular epithelium): chemical messengers

• Integrity of barrier maintained by: 1. Intercellular connections 2. Attachment to the basement membrane 3. Epithelial maintenance and repair

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4-2 Epithelial Tissue Intracellular Connections • For Both Support & Communication (2 types) • A. General Adhesion: Large Connections 1. CAMs (cell adhesion molecules): • Connect adjacent membranes or binds extracellular materials (e.g. basal lamina)

2. Intercellular cement: • Thin layer of proteoglycans + glycosaminoglycans (GAGs) such as hyaluronan – Attach adjacent membranes

• B. Specific Adhesion = Cell Junction 1. Tight Junctions 2. Gap Junctions 3. Desmosomes

Figure 4-2 Cell Junctions

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4-2 Epithelial Tissue Cell Junctions: Tight Junctions • Between two plasma membranes • Interlocking junctional proteins bind lipid portion of membrane producing a water tight seal

Figure 4-2 Cell Junctions

• Prevents passage of water and solutes • Isolates wastes in lumen • Just inferior (deep) to the tight junction, an adhesion belt consisting of CAMs bind to the microfilaments of the terminal web

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4-2 Epithelial Tissue Cell Junctions: Gap Junctions • Connexons form protein channels between adjacent cells that allow molecules (e.g., small ions) to pass between

Figure 4-2 Cell Junctions

• Allows for rapid communication • Cells can work in concert, for example as in the beating of cilia or contractions of the heart

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4-2 Epithelial Tissue Cell Junctions: Desmosomes Strong connections that use cell adhesion molecules (CAMs) cemented to dense areas, which attach to the cytoskeleton

Figure 4-2 Cell Junctions

• resist stretching and twisting • responsible for sheet-like properties

1.

Spot Desmosomes: • tie cells together; allow bend & twist

2.

Hemidesmosomes: • Half spot desmosome at basal surface, attaches cell to extra-cellular filaments in basal lamina

Basal Lamina Attachment Clear layer (Lamina lucida) - thin layer secreted by epithelia; barrier to proteins Dense layer (Lamina densa) - thick fibers produced by connective tissue; provide strength & a selective filtration barrier

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4-2 Epithelial Tissue Maintenance & Repair • Epithelial stem cells are anchored to lamina lucida (clear layer) • Epithelia are replaced by division of germinative cells (stem cells) • Stem cells divide and migrate toward apical region

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4-3 Classification of Epithelia • Based on shape and layers 1. Based on shape (all look hexagonal from top) •

Squamous — thin & flat; disc-shaped nucleus

•

Cuboidal — cube or square; round nucleus Columnar — tall & slender; oval nucleus

•

2. Based on layers •

•

Simple (single layer)—fairly weak; for absorption, secretion or filtration Stratified (> 1 layer)—strong; for protection

• 8 types of Epithelial Tissues… 14

4-3 Classification of Epithelia – 1. Simple Squamous • Thin & delicate • Locations: found in protected regions • Mesothelium (serosa-body cavity lining), endothelium (line blood vessels & heart), kidney tubules, cornea, and alveoli of lungs

• Functions: •

Absorption, diffusion, filtration, or secretion Figure 4-3a Squamous Epithelium

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4-3 Classification of Epithelia – 2. Stratified Squamous • Basal cells look cuboidal; apical cells - squamous • Locations: exposed surfaces (e.g., skin, mouth, throat, etc.) • Functions: protection from abrasion, pathogens & chemicals Two types: Nonkeratinized = mucosa - Must kept moist; all cells are nucleated (mouth, esophagus, anus & vagina)

Keratinized = epidermis (skin) - Dry, apical cells dead; keratin resists dehydration and adds strength Figure 4-3b Squamous Epithelia

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4-3 Classification of Epithelia – 3. Simple Cubiodal • Locations: Kidney tubules Pancreas Salivary glands Thyroid gland

• Functions Secretion Absorption

Figure 4-4a Cuboidal Epithelia

Figure 4-4a Cuboidal Epithelia

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4-3 Classification of Epithelia – 4. Stratified Cuboidal • Rare • Typically two layers • Locations: Some sweat glands Some mammary glands

• Functions Secretion Absorption Figure 4-4b Stratified Cuboidal Epithelium

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4-3 Classification of Epithelia – 5. Transitional •

Tolerates repeated cycles of stretching and recoiling and returns to its previous shape without damage

•

Appearance changes as stretching occurs • Relaxed: looks like stratified cuboidal; Stretched: stratified squamous

•

Location: Urinary bladder & ureters

•

Function: stretch tolerance Figure 4-4c Transitional Epithelia

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4-3 Classification of Epithelia – 6. Simple Columnar •

Nuclei line up near basal lamina

•

Apical surface typically has microvilli = “brush border” (in intestine)

•

Goblet cells, which secrete mucus, often present

•

Location: Stomach, intestine, gall bladder, uterine tubes, and collecting ducts of kidney

•

Function: Absorption and secretion Figure 4-5a Columnar Epithelia

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4-3 Classification of Epithelia – 7. Pseudostratified Ciliated Columnar • • • • • •

Several cell types: varying shapes and functions All cells contact basal lamina but some too short to reach apical surface Nuclei scattered so it appears stratified (hence “pseudostratified”) Tall cells have cilia on apical surface Goblet cells (mucus) often present Location: • Function: Nasal cavity, trachea, bronchi, Move materials Male reproductive tract, across surface Female uterine tubes Figure 4-5b Columnar Epithelia

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4-3 Classification of Epithelia – 8. Stratified Columnar • • •

•

Rare Two or more layers with only apical layer columnar Locations (tiny parts of): Pharynx, epiglottis, anus, mammary glands, salivary glands, and urethra Functions: Minor protection Figure 4-5c Columnar Epithelia

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4-3 Classification of Epithelia: Glandular • Glandular Epithelia 1. Endocrine glands: “internally secreting” • secrete into interstitial fluid (ductless)à blood • secretions = hormones • regulate and coordinate activities • e.g., pancreas, thyroid, thymus, pituitary 2. Exocrine glands: “externally secreting” • secrete into duct à epithelial surface • e.g., digestive enzymes, perspiration, tears, milk, and mucus • Classified in three ways: 1. Mode of Secretion (3) 2. Type of Secretion (3) 23 3. Structure (8)

4-3 Modes of Secretion in Exocrine Glandular Epithelia • Merocrine (mero = part) secretion • Produced in Golgi apparatus • Released by secretory vesicles (exocytosis) • e.g., mucin, sweat

• Apocrine (apo = off) secretion • Produced in Golgi apparatus • Released by shedding cytoplasm (apical) • e.g., mammary gland - milk

• Holocrine (holo = entire) secretion • Released by cells bursting, killing gland cells • Gland cells replaced by stem cells • e.g., sebaceous gland - oils 24

4-3 B. Types of Secretion in Exocrine Glandular Epithelia

1.

Serous Glands: water + enzymes • e.g., parotid salivary gland

2.

Mucus Glands: mucin (mucin + water = mucus) • e.g., goblet cell, sublingual salivary gland

3.

Mixed exocrine glands: serous + mucin secretion • e.g., submandibular salivary gland 25

4-3 C. Gland Structure of Glandular Epithelia • Two Classifications of Exocrine Glands based on Structure: • Unicellular glands (= 1 cell) • Mucous (goblet) cells are the only unicellular exocrine glands • Scattered among epithelia • For example, in intestinal lining

• Multicellular glands • groups of cells named for their • structure (simple or compound), • shape (tubular or aveolar) and • relationship between ducts and glandular areas (e.g., branched)

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4-3 Multicellular Exocrine Gland Structure Structure of the duct: a. simple (undivided) b. compound (divided)

Shape of secretory portion of the gland: a. tubular (tube shaped) b. alveolar or acinar or acinous or sacculus (blind pockets or sacs)

Relationship between ducts and glandular areas: a. branched (several secretory areas sharing one duct)

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4-4 Structure/Function of Connective Tissue Diverse Functions: • Connect epithelium to the rest of the body (basal lamina) • Provide structure (bone), store energy (fat), transport materials (blood)

Features: • Never exposed to the environment • Usually vascularized • Consists of cells in a matrix (extracellular fibers + ground substance [a fluid]), which makes up the majority of tissue volume & determines function

Basic Components: 1.

Specialized cells: Produce matrix, provide protection

2.

Extracellular protein fibers: Support, strength

3.

Ground Substance: Gel fluid, consisting of interstitial fluid, cell adhesion molecules & GAGs (glycosaminoglycans = proteoglycans that form a gel)

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4-4 Connective Tissue • Specific Functions of Connective Tissue • Establishing a structural framework for the body • Transporting fluids and dissolved materials • Protecting delicate organs • Supporting, surrounding, and interconnecting other types of tissue • Storing energy reserves, especially in the form of triglycerides • Defending the body from invading microorganisms 29

4-4 Connective Tissue: Classifications 1. Connective tissue proper • Connect and protect (e.g., adipose tissue and tendons) A. Loose connective tissue = More ground substance, less fibers (e.g., adipose tissue) B. Dense connective tissue = More fibers, less ground substance (e.g., tendons)

2. Fluid connective tissues • Transport (e.g., blood and lymph)

3. Supporting connective tissues • Structural strength (e.g., cartilage and bone) 30

4-4 Connective Tissue Proper: Cells and Fibers • Connective Tissue Proper contains: 1. Extracellular fibers 2. Ground Substance (a clear, colorless, and viscous fluid that fills spaces between cells and slows pathogen movement) 3. A Varied Cell Population (9 different types)

Figure 4-8 The Cells and Fibers of Connective Tissue Proper

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4-4 Connective Tissue Proper: 9 Cell Types 1. Fibroblasts

3. Macrophages cont.

• The most abundant cell type: • eat pathogens & damaged cells - found in all connective tissue proper - fixed macrophages stay in - secrete proteins and hyaluronan tissue (cellular cement), which makes - free macrophages migrate ground substance viscous; also 4. Adipocytes secrete protein subunits that make • Fat cells: up the extracellular fibers - each cell stores a single, large fat droplet 2. Fibrocytes • The second most abundant cell type: 5. Mesenchymal Cells - found in all connective tissue proper • Stem cells that respond to injury or - maintain the fibers of connective infection: tissue proper - differentiate into fibroblasts, macrophages, etc. 3. Macrophages • Large, amoeba-like cells of the immune 6. system:

Melanocytes

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• Synthesize and store melanin

4-4 Connective Tissue Proper: 9 Cell Types 7. Mast Cells • Stimulate inflammation after injury or infection: – release histamine and heparin – (Basophils, a type of leukocytes or white blood cells, also contains histamine and heparin that aids in the inflammatory response and tissue repair)

9. Microphages • Phagocytic white blood cells: – respond to signals from macrophages and mast cells – e.g., neutrophils and eosinophils

8. Lymphocytes • Specialized immune cells in lymphoid (lymphatic) system: – e.g., lymphocytes may develop into plasma cells (plasmocytes) that produce antibodies

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4-4 Connective Tissue Fiber Types 1. Collagen fibers: collagen protein (most common) • rope like, long, straight, unbranched • resists force in 1 direction; strong & flexible • e.g., tendons and ligaments 2. Reticular fibers: collagen protein • network of interwoven fibers (stroma) • resist force in many directions • strong & flexible • stabilize functional cells (parenchyma) and structures • e.g., sheaths around organs 3. Elastic fibers: elastin protein • branched and wavy, flexible • return to original length after stretching • e.g., elastic ligaments of vertebrae

Collagen fibers

Reticular fibers

Elastic fibers

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4-4 Embryonic Connective Tissue • Embryonic connective tissue first appears in the developing embryo as star-shaped cells in a gelatinous matrix • Mesenchyme (embryonic stem cells) • The first connective tissue in embryos • Mucous connective tissue • Loose embryonic connective tissue not found in adults

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4-4 – 1. Connective Tissue Proper (2 types) A. Loose Connective Tissues (3 subtypes) • The “packing materials” of the body • Highly vascularized; Varied cell types • Functions: • Fill space • Cushion & support tissues • Store fat • Feed epithelial layers • Three types in adults: I. Areolar (“little space”) • Least specialized • Open framework • Viscous ground substance • All fiber types, especially elastic fibers • Holds blood vessels and capillary beds • Separates skin from muscle

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4-4 – 1. Connective Tissue Proper A. Loose Connective Tissues II. Adipose Tissue • 90% adipocytes (+ mesenchymal cells for replacement) • Adult adipocytes do NOT divide, can only expand/retract Locations: deep to skin, surrounding eyeballs, kidneys, heart Functions: padding, insulation, and energy storage Two subtypes: A. White fat: triglyceride storage, insulation, shock absorber B. Brown fat: more abundant in infants, high mitochondria content for heat generation, highly vascularized for heat dissipation

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4-4 – 1. Connective Tissue Proper A. Loose Connective Tissues III. Reticular Tissue • Provides support • Complex, three-dimensional network • Supportive fibers (stroma) of organs Location: some organs --lymph nodes, bone marrow, liver, spleen Function: Support functional cells (parenchyma) Reticular Tissue

Figure 4-10b Adipose and Reticular Tissues

LOCATIONS: Liver, kidney, spleen, lymph nodes, and bone marrow FUNCTIONS: Provides supporting framework

Reticular fibers

Reticular tissue from liver

Reticular Tissue

LM ´ 375

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4-4 - 1. Connective Tissue Proper B. Dense Connective Tissues • • •

Tightly packed tissue with high numbers of collagen or elastic fibers and little ground substance Poorly vascularized Cells are primarily fibroblasts

Two Types according to current book edition: I.

Dense regular connective tissue (which includes the subtype “elastic tissue”) II. Dense irregular connective tissue 39

4-4 – 1. Connective Tissue B. Dense Connective Tissue I. Dense Regular Connective Tissue Tightly packed bundles of parallel collagen fibers, aligned with force direction Location: • Tendons attach muscles to bones • Ligaments connect bone to bone and stabilize organs • Aponeuroses attach broad flat muscles to bones or other muscles Function: • High strength attachment; stabilizes position Figure 4-11 Dense Connective Tissues

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4-4 – 1. Connective Tissue Proper B. Dense Regular Connective Tissue Elastic Connective Tissue • Made mostly of elastic fibers with some collagen Location: • Vertebral ligaments and artery walls Function: • Strength with stretch and flexibility (elasticity) Figure 4-11 Dense Connective Tissues

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4-4 – 1. Connective Tissue Proper B. Dense Connective Tissue II. Dense Irregular Connective Tissue Interwoven networks of collagen fibers Location: • • • •

forms capsules around some organs (e.g., liver, kidneys) periosteum (sheath around bone) perichondrium (around cartilage) dermis (deep skin)

Function: • resist tension from many directions; forms attachments Figure 4-11 Dense Connective Tissues

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4-4 – 2. Fluid Connective Tissue • Watery matrix of dissolved proteins • Carry specific cell types (formed elements) • Two Types: Blood & Lymph A. Blood Matrix = Plasma = serum (fluid) + plasma proteins (produced by liver) fibers are soluble until clot forms Cells = Formed elements originate from hemocytoblast (stem cells) in bone marrow Location: contained in blood vessels Function: transport nutrients, wastes and defense cells throughout the body (cardiovascular system – arteries, capillaries & veins) Plasma à Interstitial Fluid à Lymph à Plasma

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4-4 – 2. Fluid Connective Tissue A. Blood • Formed elements: Erythrocytes (red blood cells) Leukocytes (white blood cells): Neutrophils, Eosinophils, Basophils, Lymphocytes (B and T cells), Monocytes (Macrophages) Figure 4-12 Formed Elements of the Blood Platelets (carry clotting factors)

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4-4 – 2. Fluid Connective Tissue B. Lymph

• Matrix: Lymph = recollected plasma fluid from the interstitial space • Cells: Lymphocytes (immune defense) • Location: Lymphatic vessels • Function: Purify and return fluid to venous (cardiovascular) system 45

4-5 – 3. Supporting Connective Tissues • Support Soft Tissues and Body Weight (against gravity) • Strong framework, few cells (chondrocytes only), fibrous matrix A. Cartilage • Gel-type ground substance • For shock absorption and protection

B. Bone • Calcified (made rigid by calcium salts, minerals) • For weight support 46

4-5 - 3. Supporting Connective Tissues A. Cartilage Composition: • Matrix: 80% water, firm gel of glycoaminoglycans made of chondroitin sulfate and hyaluronic acid, + fibers • Cells: chondrocytes in lacunae (chambers) • Only cells in the cartilage matrix

Structure: • No innervation • Avascular (no blood vessels) • chondrocytes produce antiangiogenesis factor • Surrounded by Perichondrium: • Outer fibrous layer = dense irregular connective tissue – Function: strength, protection, attachment • Inner cellular layer (fibroblasts) – Function: growth and maintenance

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4-5 - 3. Supporting Connective Tissues A. Cartilage Growth – 2 Mechanisms: I. Interstitial Growth (embryos) Chondroblasts in matrix divide Daughters produce more matrix Mature cells = chondrocytes Important during development Figure 4-13a The Growth of Cartilage

Matrix

New matrix

Chondrocyte Lacuna Chondrocyte undergoes division within a lacuna surrounded by cartilage matrix.

As daughter cells secrete additional matrix, they move apart, expanding the cartilage from within.

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4-5 - 3. Supporting Connective Tissues A. Cartilage Growth II. Appositional Growth (children, minor repair in adult) New layers added by cells of inner perichondrium Serious Injury = scar; cartilage replaced by fibrous collagen Figure 4-13b The Growth of Cartilage

Dividing stem cell

Fibroblast

Perichondrium

New matrix

Chondroblasts

Cells in the cellular layer of the perichondrium differentiate into chondroblasts.

These immature chondroblasts secrete new matrix.

Immature chondrocyte Older matrix Mature chondrocyte As the matrix enlarges, more chondroblasts are incorporated; they are replaced by divisions of stem cells in the perichondrium.

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4-5 – 3. Supporting Connective Tissues A. Cartilage Types (3) I. Hyaline cartilage: • •

Contains fine, closely packed collagen fibers Tough, springy Location: • Synovial joints, rib tips - sternum and trachea • Articular surfaces have no perichondrium Function: • Provide stiff flexible support • Reduce friction between bones Figure 4-14a Types of Cartilage

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4-5 – 3. Supporting Connective Tissues A. Cartilage Types (3)

II. Elastic cartilage: • •

Matrix contains tightly packed elastic fibers Flexible support Location: • Auricle (external) of ear, epiglottis Function: • Support but resilient, flexible and shape holding support Figure 4-14b Types of Cartilage

Elastic Cartilage LOCATIONS: Auricle of external ear; epiglottis; auditory canal; cuneiform cartilages of larynx FUNCTIONS: Provides support, but tolerates distortion without damage and returns to original shape

Chondrocyte in lacuna

Elastic fibers in matrix

Elastic cartilage

LM ´ 358

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4-5 – 3. Supporting Connective Tissues A. Cartilage Types (3)

III. Fibrocartilage: • •

Matrix contains dense interwoven collagen fibers with little ground substance Tough, durable Location: Function: • Knee (meniscus) • Limits movement • Pubic symphysis, knee joint • Absorbs Shock: Pads • Intervertebral discs • Prevents bone-to-bone contact Figure 4-14c Types of Cartilage

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4-5 – 3. Supporting Connective Tissues B. Bone or Osseous Tissue • Strong (calcified calcium salt deposits) • Resists shattering (flexible collagen fibers) • Highly vascularized with little ground substance Matrix: • 2/3 calcified: calcium salts deposits for strength • Calcium phosphate + calcium carbonate • 1/3 collagen for flexibility to resist shatter

• Bone Cells or Osteocytes • Located in lacunae arranged around central canals within matrix • Small channels through matrix (canaliculi) access blood supply • Canaliculi necessary for nutrient and waste exchange, no diffusion through calcium 53

4-5 – 3. Supporting Connective Tissues B. Bone or Osseous Tissue

• Periosteum (dense, irregular connective tissue) • Covers bone surfaces • Outer Fibrous layer for attachment (surrounding tissue as well as tendons & ligaments) • Inner cellular layer for growth (appositional) and repair Location: Bones Function: Support & Protection; Levers for movement Storage of minerals Figure 4-15 Bone

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4-5 – 3. Supporting Connective Tissues Comparison of (A) Cartilage & (B) Bone

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4-6 Membranes • Membranes • Are physical barriers • Line or cover portions of the body • Consist of an epithelium supported by connective tissues

Four Types of Membranes 1. Mucous membranes 2. Serous membranes 3. Cutaneous membrane 4. Synovial membranes

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4-6 Membranes 1. Mucous Membranes (Mucosae) • Consist of epithelium + areolar connective tissue called lamina propria • Line passageways that have external connections • In digestive, respiratory, urinary, and reproductive tracts • Epithelial surfaces must be moist

• To reduce friction • To facilitate absorption and excretion Figure 4-16a Membranes

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4-6 Membranes 2. Serous Membranes • Consist of Mesothelium + areolar connective tissue • Line cavities not open to the outside Figure 4-16b • Are thin but strong • Have fluid transudate to reduce friction • Membrane has two portions: • parietal portion covering the cavity wall • visceral portion (serosa) covering the organs

Membranes

Three Types of Serous Membranes A. • • B. • •

Pleura: Lines pleural cavities Covers lungs Peritoneum: Lines peritoneal cavity Covers abdominal organs

C. Pericardium: • Lines pericardial cavity • Covers heart

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4-6 Membranes 3. Cutaneous Membrane • Epidermis + dermis = “skin” • Keratinized stratified squamous epithelium + areolar and dense irregular connective tissue • Thick, waterproof, and dry (only dry membrane) Figure 4-16c & d

Membranes

4. Synovial Membranes • Areolar connective tissue with woven collagen, proteogycans and glycoproteins in matrix • Line moving, articulating joint cavities • Produce synovial fluid (lubricant) • Protect the ends of bones • Lack a “true" epithelium

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4-7 Internal Framework of the Body •

Connective Tissues 1. Provide strength and stability 2. Maintain positions of internal organs 3. Provide routes for blood vessels, lymphatic vessels, and nerves

•

Fasciae Singular form = fascia • •

The body’s framework of connective tissue Layers and wrappings that support or surround organs

• Three Types of Fasciae 1. Superficial fascia (insulation & padding) 2. Deep fascia (anchors, resists force) 3. Subserous fascia (prevents distortion)

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Figure 4-17 The Fasciae

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4-8 Muscle Tissue • Classification of Muscle Cells • Striated (muscle cells with a banded appearance) • Nonstriated (not banded; smooth) • Muscle cells can have a single nucleus or be multinucleate • Muscle cells can be controlled voluntarily (consciously) • Muscle cells can be controlled involuntarily (automatically) 62

4-8 Muscle Tissue 1. Skeletal Muscle Cells: Striated, voluntary, multinucleated Cells = fibers • Up to 1 ft long (e.g., soleus muscle of basketball player) • No cell division • Appear striated: actin and myosin organized into myofibrils

Myosatellite cells (stem cells) present for minor repair Location: skeletal muscles (‘meat’) Function: Move skeleton, Guard entrances/exits, Generate heat Figure 4-18a Muscle Tissue

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4-8 Muscle Tissue 2. Cardiac Muscle Cells = Cardiocytes • • • •

Striated, involuntary, mono- or multi-nucleated Long, Branched cells No cell division Neighboring cells connected by intercalated discs: • Desomosomes + intracellular cement + gap junctions • Gap junctions help coordinate contractions (ion exchange)

• Overall pace regulated by pacemaker cells Figure 4-18b Muscle Tissue

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4-8 Muscle Tissue 3. Smooth Muscle Cells • Nonstriated, involuntary, single nucleus • Cells: small, spindle shaped • Myofibrils poorly organized so no striations • Capable of cell division

Location: walls of blood vessels and hollow organs (e.g., digestive, respiratory, urinary & reproductive tracts) Functions: move materials through the organ Figure 4-18c Muscle Tissue

Smooth Muscle Tissue Cells are short, spindle-shaped, and nonstriated, with a single, central nucleus. LOCATIONS: Found in the walls of blood vessels and in digestive, respiratory, urinary, and reproductive organs FUNCTIONS: Moves food, urine, and reproductive tract secretions; controls diameter of respiratory passageways; regulates diameter of blood vessels

Nucleus

Smooth muscle cell

Smooth muscle

LM ´ 235

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4-9 Neural Tissue Function: • specialized for conducting electrical (nervous) impulses • rapidly senses internal or external environment • process information and controls responses

Location: • Most in brain and spinal cord: Central Nervous System • 2% in Peripheral Nervous System

Cell Types: • Neuroglia Cells: • Support, repair, and supply nutrients to nervous tissue

• Neurons: • • • •

• Many dendrites: receive info Transmit information • One axon: transmits info Up to 3 ft long • No cell division Large soma (cell body) 66 Large nucleus, visible nucleoli

4-9 Neural Tissue: Cell Parts • Cell body • Contains the nucleus and nucleolus

• Dendrites • Short branches extending from the cell body • Receive incoming signals

Figure 4-19 Neural Tissue

• Axon (nerve fiber) • Long, thin extension of • the cell body • Carries outgoing electrical signals to their destination 67

4-10 Tissue Injuries and Repair • Tissues respond to injuries to maintain homeostasis • Cells restore homeostasis with 2 processes: • Inflammation • Regeneration (repair)

Inflammation: • Prevent spread of injury (trauma) or infection (pathogens) • Characterized by: swelling, redness, warmth and pain • Process to remove necrotic cells and infectious agents

Regeneration: • Replacement of collagen with original tissue type

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4-10 Tissue Injuries and Repair • Inflammatory Response • Can be triggered by: • Trauma (physical injury) • Infection (the presence of harmful pathogens)

• Damaged cells release chemical signals into the surrounding interstitial fluid • Prostaglandins • Proteins • Potassium ions

• As cells break down: • Lysosomes release enzymes that destroy the injured cell and attack surrounding tissues • Tissue destruction is called necrosis

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4-10 Tissue Injuries and Repair: Inflammation • Necrotic tissues and cellular debris (pus) accumulate in the wound

• Abscess – pus trapped in an enclosed area • Injury stimulates mast cells to release: • Histamine • Heparin • Prostaglandins

• Dilation of blood vessels

• • • •

Increases blood circulation in the area Causes warmth and redness Brings more nutrients and oxygen to the area Removes wastes 70

4-10 Tissue Injuries and Repair • Plasma diffuses into the area • Causes swelling and pain

• Phagocytic white blood cells • Clean up the area

• Regeneration • When the injury or infection is cleaned up • Healing (regeneration) begins

• The Process of Regeneration • Fibroblasts move into necrotic area • Lay down collagen fibers • To bind the area together (scar tissue)

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4-10 Tissue Injuries and Repair • The Process of Regeneration Cont. • New cells migrate into area • Or are produced by mesenchymal stem cells

• Not all tissues can regenerate • Epithelia and connective tissues regenerate well • Cardiac cells and neurons do not regenerate (or regenerate poorly)

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Figure 4-20 Tissue Repair

Mast Cell Activation

stimulates

When an injury damages connective tissue, mast cells release a variety of chemicals. This process, called mast cell activation, stimulates inflammation.

Mast cell

Exposure to Pathogens and Toxins Injured tissue contains an abnormal concentration of pathogens, toxins, waste products, and the chemicals from injured cells. When a tissue is injured, a general defense mechanism is activated.

73

Figure 4-20 Tissue Repair

Mast Cell Activation When an injury damages connective tissue, mast cells release a variety of chemicals. This process, called mast cell activation, stimulates inflammation.

Mast cell Histamine Heparin Prostaglandins

INFLAMMATION Inflammation produces several familiar indications of injury, including swelling, redness, warmth, and pain. Inflammation may also result from the presence of pathogens, such as harmful bacteria, within the tissues; the presence of these pathogens constitutes an infection.

Increased Blood Flow

Increased Vessel Permeability

Pain

In response to the released chemicals, blood vessels dilate, increasing blood flow through the damaged tissue.

Vessel dilation is accompanied by an increase in the permeability of the capillary walls. Plasma now diffuses into the injured tissue, so the area becomes swollen.

The abnormal conditions within the tissue and the chemicals released by mast cells stimulate nerve endings that produce the sensation of pain.

PAIN 74

Figure 4-20 Tissue Repair

Increased Local Temperature

Increased Oxygen and Nutrients

Increased Phagocytosis

Removal of Toxins and Wastes

The increased blood flow and permeability causes the tissue to become warm and red.

Vessel dilation, increased blood flow, and increased vessel permeability result in enhanced delivery of oxygen and nutrients.

Phagocytes in the tissue are activated, and they begin engulfing tissue debris and pathogens.

Enhanced circulation carries away toxins and waste products, distributing them to the kidneys for excretion, or to the liver for inactivation.

O2

Toxins and wastes

Regeneration

Regeneration is the repair that occurs after the damaged tissue has been stabilized and the inflammation has subsided. Fibroblasts move into the area, laying down a collagenous framework known as scar tissue. Over time, scar tissue is usually “remodeled” and gradually assumes a more normal appearance.

Inflammation Subsides Over a period of hours to days, the cleanup process generally succeeds in eliminating the inflammatory stimuli.

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Figure 4-20 Tissue Repair

Normal tissue conditions restored

Inhibits mast cell activation

Regeneration Regeneration is the repair that occurs after the damaged tissue has been stabilized and the inflammation has subsided. Fibroblasts move into the area, laying down a collagenous framework known as scar tissue. Over time, scar tissue is usually “remodeled” and gradually assumes a more normal appearance.

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4-11 Aging and Tissue

Hallmarks of Cancer: Sustain proliferative signals Evade growth suppressors Resist cell death Enable replicate immortality Induce angiogenesis Activate Invasiveness

• Speed & efficiency of tissue repair decrease with age, due to: • Slower rate of energy consumption (metabolism) • Hormonal alterations • Reduced physical activity • Effects of Aging • Chemical and structural tissue changes • Thinning epithelia and connective tissues • Increased bruising and bone brittleness • Joint pain and broken bones • Cardiovascular disease • Mental deterioration • Cancer rates increase with age • 25% of all people in the United States develop cancer • Cancer is the #2 cause of death in the United States • Environmental chemicals and cigarette smoke cause cancer • Carcinoma (epithelia), sarcoma (connective), blastoma (precursor cells), lymphoma & leukemia (-blood forming cells), etc.

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Chapter 4 Summary • Organization of specialized cells into tissues: • • • •

epithelial tissue connective tissue muscular tissue nervous tissue

• Division of epithelial tissues into epithelia and glands: • epithelia as avascular barriers for protection • glands as secretory structures

• Specializations of epithelial cells for sensation or motion:

• microvilli • cilia 78

Chapter 4 Summary • Attachments of epithelia to other cells and underlying tissues: • polarity (apical surface and basal lamina) • cell adhesion molecules (CAMs) • cell junctions (tight junctions, gap junctions and desmosomes)

• Maintenance of epithelia: • germinative cells & stem cells

• Classification of epithelial cells: • by number of cell layers (simple or stratified) • by shape of cells (squamous, columnar or cuboidal) 79

Chapter 4 Summary • Classification of epithelial glands: • • • •

by method of secretion (exocrine or endocrine) by type of secretions (merocrine, apocrine, holocrine) by organization (unicellular or multicellular) by structure (related to branches and ducts)

• The functions of connective tissues: • Structure, transport, protection, support, connections, and energy storage

• The structure of connective tissues: • Extracellular fibers + ground substance (= matrix) + specialized cells 80

Chapter 4 Summary • The classification of connective tissues: • connective tissue proper (cell types, fiber types, and embryonic connective tissues) • fluid connective tissues (blood and lymph, fluid transport systems) • supporting connective tissues (cartilage and bone)

• The 4 types of membranes that cover and protect organs: • • • •

mucous membranes (lamina propria) serous membranes (transudate) cutaneous membrane (skin) synovial membrane (encapsulating joints)

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Chapter 4 Summary • The fasciae (superficial, deep and subserous) • The 3 types of muscle tissues (skeletal, cardiac, and smooth) • The classification of muscle tissues by striation, nucleation, and voluntary control • The 2 types of cells in neural tissue: • neurons and neuroglia

• The parts of a neuron (nerve cell): • cell body, dendrites, and axon (nerve fiber)

• Tissue injuries and repair systems (inflammation and regeneration) • The relationship between aging, tissue structure, and cancer 82