Chapter 4:

The Tissue Level of Organization

Introduction

• Tissue:– Collection of specialized cells that

perform limited number of functions

• Histology:– The study of tissues

What are the four tissues of the body?

The four tissues of the Body

• Epithelial Tissue: “covering”– Covers exposed surfaces– Lines internal passageways – Forms glands

• Connective Tissue: “support” – Fills internal spaces– Provides structure and strength to

support other tissues– Transports materials– Stores energy

The four tissues of the Body

• Muscle Tissue: “movement”– Specialized for contraction – Skeletal muscle, heart muscle, and walls

of hollow organs

• Neural Tissue: “control”– Carries electrical signals from 1 part of

the body to another

Primary Germ Layer• Embryonic layers give rise to all four

tissue types in adults– Ectoderm: nervous, epithelial (epidermis)– Mesoderm: muscle, connective, epithelial

(endothelium + mesothelium)– Endoderm: epithelial (mucosa)

KEY CONCEPT

• Tissues are collections of cells and cell products that perform specific, limited functions

• 4 tissue types form all the structures of the human body: – epithelial, connective, muscle, and

neural

Epithelial Tissues

• 2 categories:– Epithelia:

• layers of cells covering internal or external surfaces

– Glands: • structures that produce fluid secretions

Special structures and functions of

Epithelial Tissues.

Characteristics of EpitheliaStructures of Epithelia:• Cellularity:

• little extracellular matrix, mostly cells• Contacts:

• cells linked by tight junctions• Polarity:

• apical + basal surfaces, separate functions• Attachment:

• attached to connective tissue (CT) via basal lamina

• Avascularity: • diffusion of CT

• Regeneration: • high turnover, stem cells at basal surface

Characteristics of Epithelia

Functions of Epithelia:• Provide physical protection:

• abrasion, dehydration, infection

• Control permeability: • semi-permeability, covers all surfaces

• Provide sensation: • sensory neurons

• Produce specialized secretions (glandular epithelium): • protection, chemical messengers

Figure 4–1

Free Surface and Attached Surface

1. Apical Surface: exposed to environment, may have:

• Microvilli: absorption or secretion • Cilla: fluid movement

2. Basolateral Surface: attachment to neighboring cells via intercellular connections

Intercellular Connections• Support and communication• General Adhesion: Large

Connections1. CAMs (cell adhesion molecules):

• Connect adjacent membranes or binds extracellular materials (e.g. basal lamina)

2. Intercellular cement:• Thin layer of hyaluronan (proteoglycan):

– Attach adjacent membranes

• Specific Adhesion=Cell Junctions1.Tight Junctions2.Gap Junctions3.Desmosomes

Cell Junctions

• Form bonds with other cells or extracellular material:

– Tight Junctions: • interlocking proteins, bind lipid portion of

membrane, water tight seal

– Gap Junctions:• connexons form channel, allow molecules to

pass for communication

– Desmosomes:• CAMs + intercellular cement on dense area

attached to cytoskeleton, resist stretching and twisting

Tight Junctions

• Between 2 cell membranes

• interlocking proteins, bind lipid portion of membrane, water tight seal

• Prevents passage of water and solutes

Figure 4–2b

Gap Junctions

Connexons form protein channels, allow molecules to pass for communication– Rapid communication

• Allow ions to pass • Coordinated

contractions in heart muscle

Figure 4–2c

Desmosomes

Cell Adhesion Molecules + intercellular cement on dense area are attached to the cytoskeleton

- resist stretching and twisting

1. Belt Desmosomes: -continuous band in apical region, attached to

microfilaments2. Button Desmosomes:

- “spot weld”, attached to intermediate filaments

3. Hemidesmosomes: - Half button desmosome at basal surface, attaches to basal lamina

Figure 4–2d

Basal Lamina (a.k.a. basement membrane)

• Lamina lucida: – Produced by epithelia– Glycoproteins + fine filaments restrict large

molecule movement• Lamina densa:

– Produced by connective tissue– Coarse protein fibers– Provides strength and filtration

Repairing and Replacing Epithelia

• Epithelia stem cells are anchored to lamina lucida

• Epithelia are replaced by division of germinative cells (stem cells)– Stem cells divide and migrate toward

apical region

Classes of Epithelia• Based on shape and layers• Shape: (all are hexagonal from the top)

1. Squamous: flat, disc shaped nucleus2. Cuboidal: cube or square, center round

nucleus3. Columnar: tall, basal oval nucleus

Table 4–1

Layers

• Simple epithelium: – single layer of cells– Function:

• absorption, secretion, filtration

• Stratified epithelium:– 2 or more layers of cells– Function:

• Protection**In stratified, name for apical cell shape**

1. Simple squamous epithelium2. Stratified squamous epithelium3. Simple cuboidal epithelium4. Stratified cuboidal epithelium5. Transitional epithelium6. Simple columnar epithelium7. Pseudostratified columnar

epithelium8. Stratified columnar epithelium

Eight Types of Epithelial Tissues

Figure 4–3a

1. Simple Squamous Epithelium

• Thin, delicate• Locations: found in protected regions

– Mesothelium (serosa), endothelium (blood vessels, heart), kidney tubules, cornea, and alveoli of lungs

• Functions:– Absorption, diffusion, filtration, or secretion

Figure 4–3b

2. Stratified Squamous Epithelium

• Basal cells look cuboidal, apical cells squamous• Found on exposed surfaces• Functions: provide protection from abrasion, pathogens, and chemicals• Two types:

A. Nonkeratinized = mucosa- Kept moist- All cells are nucleatedLocation: mouth, esophagus, anus, and vagina

B. Keratinized = epidermis- dry, apical cells dead- cells contain keratin protein to resist dehydration and adds strength

3. Simple Cuboidal Epithelia• Location: * Functions:

– Kidney tubules - Secretion– Pancreas -Absorption– Salivary glands– Thyroid

4. Stratified Cuboidal Epithelium

• Rare• Typically 2 layers• Location: * Function:

– Some sweat glands - Secretion– Some mammary glands - Absorption

Figure 4–4b

5. Transitional Epithelium

• Relaxed: looks like stratified cuboidal• Stretched: looks squamous• Location: * Function

– Urinary bladder - tolerate excessive stretching

– Ureters

Figure 4–4c

Columnar Epithelia

• Simple columnar epithelium:– absorption and secretion

• Pseudostratified columnar epithelium:– cilia movement

• Stratified columnar epithelium:– protection

6. Simple Columnar Epithelium

• Nuclei line up near the basal lamina• Apical surface of cells often has microvilli = “brush

border” (in intestine)• Goblet cells often present: secrete mucus• Locations:

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

• Functions:– Absorption or secretion

Figure 4–5a

7. Pseudostratified Columnar Epithelium

• Several cell types: varying shapes and functions• All cells contact basal lamina• Some too short to reach apical surface• Nuclei scattered so it appears stratified• Tall cells have cilia on apical surface• Goblet cells (mucus) often present• Location: Function:

– Nasal cavity, trachea, bronchi - move material – Male reproductive tract across surface– Female uterine tubes

Figure 4–5b

8. Stratified Columnar Epithelium

• Rare• Two layers or multiple 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

Glandular EpitheliaFor secretion, makes up glands

1. Endocrine glands: “internally secreting”-secrete into interstital fluid blood

-secretions = hormones -regulate and coordinate activities e.g. pancreas, thyroid, thymus, pituitary

2. Exocrine glands: “externally secreting” -secrete into duct epithelial surface -e.g. digestive enzymes, perspiration, tears, milk,

and mucus -Classified three ways:

1. Mode of Secretion 2. Type of Secretion 3. Structure

A. Modes of Secretion1. Merocrine secretion:

-product released from secretory vesicles by exocytosis-e.g. mucus, sweat

2. Apocrine Secretion: - product accumulates

in vesicles - apical region of cell

which vesicles is shed to release product-e.g. milk

Figure 4–6a

Modes of Secretion3. Holocrine secretion

- product accumulates in vesicles- whole cell is lysed to release product- cell dies, must be replaced by stem cells

e.g. sebum

Figure 4–6c

B. Types of Secretion

1. Serous Glands: water + enzymes- e.g. parotid salivary gland

2. Mucus Glands: mucin (+water = mucus)

- e.g. goblet cell3. Mixed exocrine glands: (serous + mucus secretion)

-e.g. submandibular salivary gland

C. Gland Structure

• Exocrine glands can be classified as:– unicellular glands: 1 cell

• E.g. goblet cell which are scattered among epithelia

– Found in intestinal lining

– multicellular glands: group of cells named for shape and structure

Structure of Multicellular Exocrine Glands

• Structural classes of exocrine glands

Figure 4–7 (1 of 2)

Simple Glands = undivided

tube shape blind pockets chamberlike

Structure of Multicellular Exocrine Glands

Figure 4–7 (2 of 2)

Compound Glands = Divided

tube shaped blind pockets chamberlike

Which of the following is NOT a characteristic of epithelial

tissue?

A. It is composed entirely of cells.

B. It stores energy reserves.C. It is avascular.D. It is capable of

regeneration.

An epithelial surface bears many microvilli. What is the

probable function of this epithelium?

A. absorptionB. secretionC. transportationD. sensation

What is the functional significance of gap junctions?

A. They maintain water-tight passages.

B. They resist stretching and twisting.

C. They coordinate the function of tissue.

D. They attach cells to extracellular matrix.

Using a light microscope, you examine a tissue and see a simple squamous epithelium on the outer

surface. Can this be a sample of the skin

surface?

A. YesB. No

Why do the pharynx, esophagus, anus, and vagina

have the same epithelial organization?

A. All are subject to mechanical trauma.

B. All are subject to abrasion.

C. All must be able to expand.

D. A and B are correct.

The secretory cells of sebaceous glands fill with secretions and then rupture, releasing their contents.

Which type of secretion is this?

A. acinarB. apocrineC. merocrineD. holocrine

A gland has no ducts to carry the glandular secretions, and the gland’s secretions are released directly into

the extracellular fluid. Which type of gland is this?

A. exocrine glandB. endocrine glandC. acinar glandD. tubular gland

Structures and functions of different

types of Connective Tissues.

Connective Tissues• Features:

– Never exposed to the environment– Usually vascularized– Consists of cells in a matrix

• Components:1. Specialized cells:

- Produce matrix, provide protection2. Extracellular protein fibers:

- Support, strength3. Ground Substance:

- gel fluid, consists of: * interstitial fluid, cell adhesion

molecules, and GAGs (glycosaminoglycans)

- proteoglycans that form a gelFibers + Ground Substance = Matrix

The Matrix

• The extracellular components of connective tissues (fibers and ground substance):– majority of cell volume– determines specialized function

Functions of Connective Tissue

1. Establish structural framework2. Transport fluid and dissolved materials3. Protect organs4. Support, surround, interconnect

tissues5. Store energy reserves6. Insulate body7. Defend against pathogens

Classification of Connective Tissues

• Connective tissue proper:– Many cell types and fiber types in thick

ground substancea. Loose: open fiber frameworkb. Dense: tightly packed fibers

• Fluid connective tissues:– May cell types in watery matrix with soluble

fibers

• Supportive connective tissues:– Limited cell population in tightly packed

matrix

Connective Tissues Derived from Mesenchyme

Embryonic CT: - mesenchymal cells in gelatinous matrix with fine fibers

1. Connective Tissue Proper• Viscous ground substance• Varied extracellular fibers• Varied cell population

Ground substance: rich in GAG -viscous, prevents microbe penetration

Fiber types:1. Collagen fibers: collagen protein2. Reticular fibers: collagen protein3. Elastic fibers: elastin protein

Figure 4–8

1. Connective Tissue ProperFiber types: 1. Collagen fibers: collagen protein -rope like, long, straight -resists force -most common 2. Reticular fibers: collagen protein -branchy, forms framework -framework of an organ = stroma (functional cells of an organ = parenchyma) 3. Elastic fibers: elastin protein

-wavy, flexible- Designed to stretch

8 Cell Types of Connective Tissue Proper

• Fibroblasts• Macrophages• Adipocytes• Mesenchymal

cells

• Mast cells• Lymphocytes• Microphages

Cell Types of CT Proper1. Fibroblasts:

- most common, most abundent - secretes ground substance:

hyaluronan + protein = GAGs - secrete fiber proteins (collagen, elastin)

- some specialized types: chondrocytes (cartilage) osteocytes (bone)

2. Mesenchymal Cells:- stem cells - differentiate to replace CT cells after

Injury (e.g. fibroblasts, adipocytes)3. Adipocytes (fat cells):

- store triglycerides- organelles pushed to periphery-number, size and location of cells varies

4. Macrophages:- phagocytic for defense

- (eat pathogens and damaged cells) - some fixed in tissues- others migrate from blood to tissues after injury

Cell Types of CT Proper5. Microphages:

- neutrophils and eosinophils- phagocytic- migrate from: blood to site of injury

6. Lymphocytes: B and T cells- involved in immune response- make antibodies

- attack foreign cells- increased number during infection- constantly migrate between: - blood and tissues and lymph

7. Mast cells:- contain histamine and heparin- stimulate inflammation in response to injury

Categories of Connective Tissue Proper

• Loose connective tissue:– more ground substance, less fibers – e.g., fat (adipose tissue)

• Dense connective tissue:– more fibers, less ground substance– e.g., tendons

A. Loose Connective Tissue

• Highly vascularized• Varied cell types• Functions:

– Fill space– Cushion & support tissues– Store fat– Feed epithelial layers

• Three types:1. Areolar CT2. Adipose Tissue3. Reticular Tissue

A. Loose Connective Tissue:Areolar CT

1. Areolar CT– Most common– Least specialized– Open framework:

• Matrix mostly ground substance– All fiber types– Location: deep to epithelium– Functions:

• Reservoir for water and salts• Absorbs shock and distortion• Fills space• Feeds epithelium

A. Loose Connective Tissue:Adipose Tissue

2. Adipose Tissue-90% adipocytes- Locations: - deep to skin, surrounding eyeballs, kidneys, heart- Functions: - padding, insulation, and energy storage-Two types: - White fat: adults, triglyceride storage, insulation - Brown fat: infants, high mitochondria content for

heat generation

A. Loose Connective Tissue:Adipose Tissue

3. Reticular Tissue -stroma (supportive fibers) of organs

-consists of reticular fibers Locations: some organ e.g. lymph nodes, bone marrow, liver Function: support parenchyma (functional) cells

B. Dense Connective Tissue

• Poorly vascularized• Mostly fibers, little ground

substance• Only fibroblasts• Three types:

1. Dense Regular CT2. Dense Irregular CT3. Elastic CT

B. Dense Connective TissueDense Regular CT

1. Dense Regular CT-bundles of parallel collagen fiber, aligned with direction of force-Location:

- tendons (muscle to bone) - ligaments (bone to bone) - muscle coverings and fascia

-Function:- high strength attachment- stabilize positions

B. Dense Connective TissueDense Irregular CT

2. Dense Irregular CT- mesh of collagen fibers- Location:

-capsules of organs-perioteum (sheath around bone)-perichondrium (around cartilage-dermis (deep skin)

-Function:-resist tension from

many directions-attachment

*Strength in Many Directions

B. Dense Connective TissueElastic CT

1. Elastic CT:-mostly elastic fibers, some collagen-Location:

-vertebral ligaments and artery walls-Function: Strength with stretch and flex

Figure 4–11c

Fluid Tissue Transport Systems

• Cardiovascular system (blood):– arteries– capillaries– veins

• Lymphatic system (lymph):– lymphatic vessels

Fluid Connective Tissues• Fluid connective tissues: 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

Plasma Interstitial Fluid Lymph Plasma

Formed Elements of Blood

• Erythrocytes (RBCs): carry oxygen• Leukocytes (WBCs): defense

– Neutrophils, Eosinophils, Basophils, Lymphocytes (B and T cells), Monocytes (Macrophages)

• Platelets: carry clotting factors

Figure 4–12

Fluid Connective Tissues

B. Lymph:-Matrix: lymph (recollected plasma fluid)-Cells: lymphocytes (immune defense)-Location:

-contained in lymphatic vessels-Function:

-purify and return fluid to blood

Lack of vitamin C in the diet interferes with the ability of

fibroblasts to produce collagen. What effect might this

interference have on connective tissue?

A. Tissue is unable to phagocytose.

B. Tissue is unable to produce melanin.

C. Tissue is weak and prone to damage.

D. Tissue is unable to produce heparine.

Many allergy sufferers take antihistamines to relieve their

allergy symptoms. Which type of cell produces the molecule that this

medication blocks?

A. eosinophilsB. mast cellsC. basophilsD. B and C

Which type of connective tissue contains primarily

triglycerides?

A. areolarB. adiposeC. reticularD. mesenchyme

Supportive Connective Tissues

• Strong framework, few cells, fibrous matrix• Function: support and shape• Mature cells in lacunae• Two types:

1. Cartilage: • gel-type ground substance• for shock absorption and protection

2. Bone: • calcified (made rigid by calcium salts, minerals)• for weight support

1. Cartilage

• Composition:– Matrix: 80% water, firm gel of glycoaminoglycans

made of chondroitin sulfate and hyaluronic acid, + fibers

– Cells: chondrocytes in lacunae (chambers)• Cells formed the matrix

• Structure:– No innervation– Avascular (no blood vessels)

• chondrocytes produce antiangiogenesis factor– Surrounded by Perichondrium:

• Outer layer = dense irregular CT – Function: protection, attachment

• Inner layer = cellular (fibroblasts)– Function: growth and repair

Growth of Cartilage: Not common in adults

1. Interstitial Growth (embryos)- Chondroblasts in matrix divide- Daughters produce more matrix

- Mature cells = chondrocytes

Figure 4–13a

Cartilage Growth

2. 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

Types of Cartilage

1. Hyaline cartilage

2. Elastic cartilage

3. Fibrocartilage

Types of Cartilage1. Hyaline cartilage:

– translucent matrix• Contains fine, closely packed collagen fibers

– Tough, springy– Location:

• Ribs, nose, respiratory tract, articular surfaces – no perichondrium

– Function:• Provide stiff flexible support• Reduce friction between bones

Types of Cartilage

2. Elastic cartilage:– Matrix contains tightly packed elastic fibers– Flexible support– Location:

• Auricle (external) of ear, epiglottis

– Function:• Resilient, flexible, shape holding support

Types of Cartilage

3. Fibrocartilage:- Matrix contains dense interwoven collagen fibers

with little ground substance- tough, durable- Location: Function:

- Knee (meniscus) - Resist Compression- Pubic symphasis - Absorb Shock: Pads knee joints - Intervertebral discs - Prevents bone-to-bone contact

Figure 4–14c

2. Bone/Osseous Tissue• Highly vascularized• Little ground substance• Matrix:

– 2/3 calcified: calcium salts deposits for strength• Calcium phosphate + calcium carbonate

– 1/3 collagen for flexibility to resist shatter• Cells: Osteocytes

– Cells formed the matrix– Located in lacunae arranged around central

canals within matrix– Connected by cytoplasmic extensions that extend

through canaliculi• Canaliculi: excess blood supply

– Canaliculi necessary for nutrient and waste exchange, no diffusion through calcium

Bone/Osseous Tissue

• Surrounded by Periosteum: covers bone surfaces– Outer: fibrous layer for attachment– Inner: cellular layer for growth and repair

• Location: Bones• Function:

– Support & Protection– Levers for movement– Storage of minerals

Structures of Bone

• Osteocytes– Connected by cytoplasmic extensions that extend

through canaliculi (small channels through matrix)– Canaliculi necessary for nutrient and waste

exchangeFigure 4–15

LM X 362

Canaliculi

Osteocytesin lacunae

Matrix

Bloodvessels

Central canal

PERIOSTEUM

Fibrouslayer

Cellularlayer

Comparing Cartilage and Bone

Table 4–2

Why does cartilage heal so slowly?

A. It lacks a direct blood supply, necessary for proper healing.

B. Chondroitin sulfate prevents healing.

C. Matrix inhibits cellular regeneration.

D. Interstitial fluid, necessary for proper healing, is excluded.

If a person has a herniated intervertebral disc, which type of cartilage has been

damaged?

A. elastic cartilageB. fibrocartilageC. hyaline cartilageD. areolar cartilage

Which two types of connective tissue have a fluid matrix?

A. lymph and cartilageB. cartilage and boneC. blood and boneD. blood and lymph

Connective tissues form the

framework of the body.

Special Connective Tissue Structures

1. Fascia:– Connective tissues that provides a

framework to connect organs to the body

– Function:• provide strength and stability• maintain positions of internal organs• provides routes for blood vessels, lymphatic

vessels, and nerves

1. Fascia

• Body’s framework of connective tissue • Layers and wrappings that support or surround

organsProvides insulation and padding

Resists force and anchors position

Prevents distortion by muscles

Epithelial and connective tissues

combine to form 4 types of

membranes.

2. Membranes

• Membranes:– are physical barriers – that line or cover portions of the body

• Consist of:– an epithelium – supported by connective tissues

4 Types of Membranes

1. Mucous

2. Serous

3. Cutaneous

4. Synovial

Figure 4–16

1. Mucous Membrane

1. Mucous membranes (mucosae):– Epithelium + areolar connective tissue called lamina

propria – Line passageways that connect to external

environment– Epithelium kept moist with mucus secretions– Location:

• digestive, respiratory, urinary, and reproductive tracts

2. Serous Membranes

2. Serous Membranes/Serosa - mesothelium + areolar connective tissue

- lines body cavities to reduce friction- pleura, peritoneum, pericardium

- Double Membrane:- Parietal layer lines cavity- Visceral layer around organ

- Epithelium kept moist by serous fluid (transudate)

Figure 4–16b

Cavities and Serous Membranes

• Pleural membrane:– lines pleural cavities– covers lungs

• Peritoneum:– lines peritoneal cavity – covers abdominal organs

• Pericardium:– lines pericardial cavity– covers heart

3. Cutaneous Membrane

3. Cutaneous membrane:– Epidermis + dermis = “skin”– Keratinized stratified squamous

epithelium + areolar and dense irregular connective tissue only dry membrane• Thick and waterproof

Figure 4–16c

4. Synovial Membranes

• Areolar connective tissue with woven collagen, proteogycans and glycoproteins in matrix

• Lines joint capsules• Produce synovial fluid (lubricant)

– Reduces friction of articular (hyaline cartilage)

• Protect the ends of bones• Lack a true epithelium• Only membrane with no epithelium

Structure of Synovial Membranes

Figure 4–16d

Which cavities in the body are lined by serous

membranes?

A. cranial and abdomenalB. pleural, peritoneal, and

pericardialC. synovial and fascialD. nasal, urinary and

reproductive

The lining of the nasal cavity is normally moist, contains numerous goblet cells, and rests on a layer of connective tissue called the lamina

propria. Which type of membrane is this?

A. mucousB. serousC. cutaneousD. synovial

A sheet of tissue has many layers of collagen fibers than run in different

directions in successive layers. Which type of tissue is this?

A. fasciaB. cutaneousC. parietalD. synovial

Muscle Tissue

• Function: Provide Movement– Is specialized for contraction

• Features:– Highly vascularized– Contains actin and myosin for

contraction

Structures and functions of the three

types of muscle tissue.

Three Muscle Types

1. Skeletal Muscle

2. Cardiac Muscle

3. Smooth Muscle

Classification of Muscle Cells

• Striated (muscle cells with a banded appearance): – or nonstriated (not banded)

• Muscle cells can have a single nucleus: – or be multinucleate

• Muscle cells can be controlled voluntarily (consciously):– or involuntarily (automatically)

3 Types of Muscle Tissue

1. Skeletal muscle: Striated, voluntary, and multinucleated– Cells = fibers

• Up to 1 ft long• Multinuclear• No cell division• Appear striated: actin and myosin organized into myofibrils

– Some satellite cells (stem cells) present for minor repair after injury

– Location: skeletal muscles (‘meat’)– Function:

• Move skeleton• Guard entrances/exit• Generate heat

3 Types of Muscle Tissue

2. Cardiac Muscle cells: - Striated Involuntary, usually single nucleus – Cells = cardiocytes

• Long, branched• Usually single nucleus but up to 5• No cell division• Striated• Neighboring cells connected by intercalated disc:

– Desmosomes + intercellular cement + gap junctions *Desmosomes & cement:

- provide tight linkage of neighboring cells *Gap junctions: - allow exchange of ions to coordinate

contraction

Cardiac Muscle Tissue

• Striated, involuntary, and single nucleus

• Location: majority of heart• Function: move blood through body

Figure 4–18b

3 Types of Muscle Tissue3. Smooth Muscle Tissue:

- Nonstriated, involuntary, and single nucleus - Cells, small, spindle shaped - uninuclear

- capable of cell division- no striations: no myofibril organization

- Locations: - walls of blood vessels- walls of hollow organs: - digestive,respiratory,urinary,reproductive

tracts - Function: move materials through the organ

Figure 4–18c

Basic structure and role of neural tissue.

Nervous/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

• Cells:– Neuroglia Cells:

• Support, repair, and supply nutrients to nervous tissue– Neurons:

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

Cell Parts of a Neuron

• Cell body:– contains the nucleus and nucleolus

• Dendrites:– short branches extending from the cell body– receive incoming signals

• Axon (nerve fiber):– long, thin extension of the cell body– carries outgoing electrical signals to their destination

Injuries affect on tissues of the body.

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 or infection– Characterized by: swelling, redness, warmth

and pain– Process to remove necrotic cells and

infectious agents

The Process of Inflammation Damaged Cells:Release prostaglandins Undergo necrosisTrigger inflammation

Endothelial Cells:Vessels leak and plasma enters wounds delivering leukocytes and clotting proteins

Fibroblasts migrate to the wound and are stimulated to secrete collagen- form a fiber scar to reinforce the clot and begin repair

Damaged tissue is Repaired or Replaced

Repair or Replacement

• Damaged tissue is repaired or replaced depending on the injury and type of tissue– Regeneration:

• replacement of collagen with original tissue type• repair will not be visible

– Fibrosis: • Visible scar of collagen• Tissue is completely replaced by a dense collagen

patch• Tissue type function is lost at the site of the scar

Summary: Inflammation and

Regeneration

Figure 4–20

Aging and Tissue Structure

• Speed and efficiency of tissue repair decreases 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

Aging and Cancer

• Cancer rates increase with age:– 1 in 4 people in the U.S. develop

cancer– cancer is the #2 cause of death in the

U.S.– environmental chemicals and

cigarette smoke can cause cancer

Injury and Cancer• Repeat or chronic

– Inflammation causes damage

• Dysplasia: change in normal shape, size, organization of tissue cells (reversible)

• Metaplasia: more serious changes, abnormal division of stem cells (reversible)

• Anaplasia: breakdown of tissue organization, genetic abnormalities of stem cells (irreversible)

• Cancer = uncontrolled growth

Which type of muscle tissue has small, tapering cells with single nuclei and no obvious

striations?

A. skeletalB. cardiacC. smoothD. all of the above

A tissue contains irregularly shaped cells with many fibrous projections,

some several centimeters long. These are probably which type of

cell?

A. neurogliaB. neuronsC. myocytesD. adipocytes

If skeletal muscle cells in adults are incapable of dividing, how is

new skeletal muscle formed?

A. through the enlarging and splitting of existing cells

B. through the atrophy of existing cells

C. through the addition of new striations

D. through the division and fusion of satellite cells

If skeletal muscle cells in adults are incapable of dividing, how is

new skeletal muscle formed?

A. through the enlarging and splitting of existing cells

B. through the atrophy of existing cells

C. through the addition of new striations

D. through the division and fusion of satellite cells

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

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)

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:– Matrix, ground substance, and protein fibers

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)

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