anatomy & physiology i lecture 3 chapter 4: tissues

Anatomy & Physiology I

Lecture 3Chapter 4: Tissues

Tissues

• Cells– Individual body cells specialized– Each type performs specific functions that maintain

homeostasis

• Tissues– Groups of cells similar in structure that perform

common or related function

• Histology – the study of tissues

© 2013 Pearson Education, Inc.

Studying Human Tissue: Microscopy

• Tissue is fixed– Preserved – FFPE or Fresh/Frozen

• Cut– Sliced thin enough to transmit photons or

electrons• Stained to enhance contrast– H&E – Hematoxylin and eosin stain– Immunohistochemisty– Specific dye to highlight cells or structures

H&E Stain

Colon tissue sectioned through the crypts

Immunohistochemistry

Stained for CD10, a marker for renal carcinoma


• Brain• Spinal cord• Nerves

Nervous tissue: Internal communication

• Muscles attached to bones (skeletal)• Muscles of heart (cardiac)• Muscles of walls of hollow organs (smooth)

Muscle tissue: Contracts to cause movement

Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters• Lining of digestive tract organs and other hollow

organs• Skin surface (epidermis)

• Bones• Tendons• Fat and other soft padding tissue

Connective tissue: Supports, protects, binds other tissues together

Figure 4.1 Overview of four basic tissue types: epithelial, connective, muscle, and nervous tissues.

Epithelial Tissue

• Sheet of cells tht covers a body surface or lines a body cavity

• Two main types (by location)• Covering and lining epithelia– On external and internal surfaces

• Glandular epithelia– Secretory tissue in glands

Epithelial Tissue

• Forms boundaries– Protection– Absorption– Filtration– Excretion– Secretion– Sensory reception

Five Characteristics

• Polarity– apical vs basal surface

• Specialized contacts– tight junctions, desmosomes

• Supported by connective tissues– for reinforcement

• Avascular, but innervated• Can regenerate

Classification of Epithelia

• All epithelial tissues have two names

• First indicates number of cell layers– Simple epithelia = single layer of cells– Stratified epithelia = two or more layers of cells

• Second indicates shape of cells– Squamous– Cuboidal– Columnar


Figure 4.2a Classification of epithelia.

Basal surfaceStratified

Classification based on number of cell layers.

Basal surfaceSimple

Apical surface

Apical surface


Cuboidal

Squamous

ColumnarClassification based on cell shape.

Figure 4.2b Classification of epithelia.

Simple Epithelia

• Functions limited due to their thickness, but nonetheless important– Absorption– Secretion– Filtration


Air sacs of lung tissue

Nuclei of squamous epithelial cells

Function: Allows materials to pass by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae.

Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae).

Description: Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia.

Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (140x).

Simple squamous epithelium

Figure 4.3a Epithelial tissues.

Simple Squamous

• Some have specialized names based on location:

• Endothelium– The lining of lymphatic vessels, blood vessels, and

heart

• Mesothelium– The epithelium of serous membranes in the ventral

body cavity


Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action.

Location: Nonciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.

Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells).

Simple columnar epithelium

Basement membrane

Photomicrograph: Simple columnarepithelium of the small intestine mucosa (660x).

Mucus of goblet cell

Simple columnar epithelial cell

Microvilli

Figure 4.3c Epithelial tissues.


Pseudostratified columnar epithelium

Function: Secrete substances, particularly mucus; propulsion of mucus by ciliary action.

Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia.

Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (800x).

Cilia

Basement membrane

Pseudo-stratified epithelial layer

Location: Nonciliated type in male’s sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract.

Trachea

Figure 4.3d Epithelial tissues.


Stratified squamous epithelium

Function: Protects underlying tissues in areas subjected to abrasion.

Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers.

Basement membrane

Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane.

Nuclei

Connective tissue

Stratified squamous epithelium

Photomicrograph: Stratified squamous epithelium lining the esophagus (285x).

Figure 4.3e Epithelial tissues.

Other Stratified Epithelia

• Stratified cuboidal and stratified columnar are rare and limited to specialized parts of body– pharynx, male urethra, some glandular ducts,

sweat and mammary glands


Transitional epithelium

Function: Stretches readily, permits stored urine to distend urinary organ.

Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch.

Location: Lines the ureters, bladder, and part of the urethra.

Transitional epithelium

Photomicrograph: Transitional epithelium lining the bladder, relaxed state (360x); note the bulbous, or rounded, appearance of the cells at the surface; these cells flatten and elongate when the bladder fills with urine.

Basement membraneConnective tissue

Figure 4.3f Epithelial tissues.

Glandular Epithelia

• Gland– One or more cells that makes and secretes an

aqueous fluid called a secretion

• Classified by– Site of product release—endocrine or exocrine– Relative number of cells forming the gland– Unicellular or multicellular

Endocrine Glands

• Ductless glands– Secretions not released into a duct, but via

exocytosis

• Secrete hormones that travel through lymph or blood to their specific target organs– every hormone has a specific target cell for a

specific physiological response

Exocrine Glands

• Secretions released onto body surfaces (skin) or into body cavities– mucous, sweat, oil, and salivary glands, digestive

juices

• More numerous than endocrine glands

• Secrete products into ducts

Unicellular Glands

• Mucous cells and Goblet cells

• Found in epithelial linings of intestinal and respiratory tracts– All produce mucin– Dissolves in water to form mucus– Slimy protective, lubricating coating


Microvilli

Golgi apparatus

Rough ER

Nucleus

Secretory vesicles containing mucin

Figure 4.4 Goblet cell (unicellular exocrine gland).

Multicellular Exocrine Glands

• Multicellular exocrine glands are more complex and specialized for the function

• Pancreas and Liver have exocrine functions despite their other roles

Connective Tissue

• Most abundant and widely distributed of primary tissues

• Four main classes– Connective tissue proper– Cartilage– Bone – Blood

Major Functions

• Binding and support• Protecting• Insulating• Storing reserve fuel• Transporting substances (blood)

Connective Tissue Elements

• Ground Substance

• Tissue Fibers

Ground Substance

• Extracellular maxtix

• Unstructured material that fills space between cells– white blood cells and immune cells migrate

• Components– Interstitial fluid– Cell adhesion proteins ("glue" for attachment) – Proteoglycans

• Protein core + large polysaccharides that trap water in varying amounts, affecting viscosity of ground substance

Connective Tissue Fibers

• Collagen– Strongest and most abundant type

• Elastic fibers– Networks of long, thin, elastin fibers that allow for

stretch and recoil

• Reticular– Short, fine, highly branched collagenous-like fibers– Form networks that offer support and elasticity

Connective Tissue Cells

• "Blast" cells – Immature form; mitotically active; secrete ground substance and fibers – Fibroblasts in connective tissue proper– Chondroblasts in cartilage– Osteoblasts in bone– Hematopoietic stem cells in bone marrow

• "Cyte" cells – Mature form; maintain matrix– Chondrocytes in cartilage – Osteocytes in bone

Connective Tissue Proper

• Loose Connective Tissue– Areolar – Adipose– Reticular

• Dense Connective Tissue– Regular– Irregular– Elastic


Connective tissue proper: loose connective tissue, areolar

Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells.

Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid.

Location: Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries.

Epithelium

Lamina propria

Photomicrograph: Areolar connectivetissue, a soft packaging tissue of the body (340x).

Elastic fibers

Ground substance

Fibroblast nuclei

Collagen fibers

Figure 4.8a Connective tissues.


Connective tissue proper: loose connective tissue, adipose

Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet.

Photomicrograph: Adipose tissue fromthe subcutaneous layer under the skin (350x).

Nucleus of adipose(fat) cell

Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs.

Location: Under skin in subcutaneous tissue; around kidneys and eyeballs; within abdomen; in breasts.

Fat dropletAdipose tissue

Mammary glands

Figure 4.8b Connective tissues.


Connective tissue proper: loose connective tissue, reticular

Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network.

Photomicrograph: Dark-staining network of reticular connective tissue fibers forming the internal skeleton of the spleen (350x).

White blood cell(lymphocyte)

Location: Lymphoid organs (lymph nodes, bone marrow, and spleen).

Spleen

Reticular fibers

Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages.

Figure 4.8c Connective tissues.


Connective tissue proper: dense connective tissue, dense regular

Description: Primarily parallelcollagen fibers; a few elastic fibers;major cell type is the fibroblast.

Function: Attaches muscles tobones or to muscles; attachesbones to bones; withstands greattensile stress when pulling force isapplied in one direction.

Location: Tendons, mostligaments, aponeuroses.

Shoulderjoint

Ligament

Tendon

Collagenfibers

Nuclei offibroblasts

Photomicrograph: Dense regular connectivetissue from a tendon (430x).

Figure 4.8d Connective tissues.


Connective tissue proper: dense connective tissue, dense irregular

Description: Primarily irregularlyarranged collagen fibers; someelastic fibers; fibroblast is themajor cell type.

Function: Withstands tensionexerted in many directions;provides structural strength.

Location: Fibrous capsules oforgans and of joints; dermis of theskin; submucosa of digestive tract.

Shoulderjoint

Fibrousjointcapsule

Photomicrograph: Dense irregular connectivetissue from the fibrous capsule of a joint (430x).

Collagenfibers

Nuclei offibroblasts

Figure 4.8e Connective tissues.


Connective tissue proper: dense connective tissue, elastic

Description: Dense regularconnective tissue containing ahigh proportion of elastic fibers.

Function: Allows tissue to recoilafter stretching; maintains pulsatileflow of blood through arteries; aidspassive recoil of lungs followinginspiration.

Location: Walls of large arteries;within certain ligaments associatedwith the vertebral column; withinthe walls of the bronchial tubes.

Photomicrograph: Elastic connective tissuein the wall of the aorta (250x).

Aorta

Heart

Elasticfibers

Figure 4.8f Connective tissues.

Cartilage

• Cells:– Chondroblasts and chondrocytes

• Tough yet flexible– Up to 80% water - can rebound after compression

• Lacks nerve fibers and blood vessels (avascular)

Cartilage

• Hyaline

• Elastic

• Fibrocartilage


Cartilage: hyaline

Description: Amorphous but firmmatrix; collagen fibers form animperceptible network;chondroblasts produce the matrixand when mature (chondrocytes)lie in lacunae.

Function: Supports and reinforces;serves as resilient cushion; resistscompressive stress.

Location: Forms most of theembryonic skeleton; covers theends of long bones in joint cavities;forms costal cartilages of the ribs;cartilages of the nose, trachea, andlarynx.

Costalcartilages Photomicrograph: Hyaline cartilage from

a costal cartilage of a rib (470x).

Matrix

Chondrocytein lacuna

Figure 4.8g Connective tissues.


Cartilage: elastic

Description: Similar to hyalinecartilage, but more elastic fibersin matrix.

Function: Maintains the shape ofa structure while allowing greatflexibility.

Location: Supports the externalear (pinna); epiglottis.

Photomicrograph: Elastic cartilage fromthe human ear pinna; forms the flexibleskeleton of the ear (800x).

Chondrocytein lacuna

Matrix

Figure 4.8h Connective tissues.


Cartilage: fibrocartilage

Description: Matrix similar to butless firm than that in hyalinecartilage; thick collagen fiberspredominate.

Function: Tensile strength allowsit to absorb compressive shock.

Location: Intervertebral discs;pubic symphysis; discs of kneejoint.

Photomicrograph: Fibrocartilage of anintervertebral disc (125x). Special stainingproduced the blue color seen.

Collagenfiber

Chondrocytesin lacunae

Intervertebraldiscs

Figure 4.8i Connective tissues.

Bone – Osseous Tissue

• Supports and protects body structures– Stores fat and synthesizes blood cells in cavities– More collagen than cartilage– Has inorganic calcium salts

• Osteoblasts produce matrix• Osteocytes maintain the matrix

• Richly vascularized


Others: bone (osseous tissue)

Description: Hard, calcifiedmatrix containing many collagenfibers; osteocytes lie in lacunae.Very well vascularized.

Function: Supports and protects(by enclosing); provides levers forthe muscles to act on; storescalcium and other minerals andfat; marrow inside bones is thesite for blood cell formation(hematopoiesis).

Location: Bones

Photomicrograph: Cross-sectional viewof bone (125x).

Lamella

Centralcanal

Lacunae

Figure 4.8j Connective tissues.

Blood

• Atypical connective tissue – is a fluid

• Red blood cells most common cell type that function in transport– Also contains white blood cells and platelets

• Fibers are soluble proteins that precipitate during blood clotting


Connective tissue: blood

Description: Red and white bloodcells in a fluid matrix (plasma).

Function: Transport respiratorygases, nutrients, wastes, and othersubstances.

Location: Contained within bloodvessels.

Photomicrograph: Smear of human blood(1670x); shows two white blood cellssurrounded by red blood cells.

Plasma

White bloodcells:• Lymphocyte• Neutrophil

Red bloodcells(erythrocytes)

Figure 4.8k Connective tissues.

Muscle

• Responsible for most types of movement– Highly vascularized

• Skeletal muscle tissue– Voluntary

• Cardiac muscle tissue– Involuntary

• Smooth muscle tissue– Involuntary


Skeletal muscle

Description: Long, cylindrical,multinucleate cells; obviousstriations.

Function: Voluntary movement;locomotion; manipulation of theenvironment; facial expression;voluntary control.

Location: In skeletal musclesattached to bones or occasionallyto skin.

Photomicrograph: Skeletal muscle(approx. 440x). Notice the obvious bandingpattern and the fact that these large cells aremultinucleate.

Striations

Nuclei

Part of musclefiber (cell)

Figure 4.9a Muscle tissues.


Cardiac muscle

Description: Branching, striated,generally uninucleate cells thatinterdigitate at specializedjunctions (intercalated discs).

Function: As it contracts, itpropels blood into the circulation;involuntary control.

Location: The walls of the heart.

Photomicrograph: Cardiac muscle (900x);notice the striations, branching of cells, andthe intercalated discs.

Striations

Nucleus

Intercalateddiscs

Figure 4.9b Muscle tissues.


Smooth muscle

Description: Spindle-shapedcells with central nuclei; nostriations; cells arranged closelyto form sheets.

Function: Propels substances orobjects (foodstuffs, urine, a baby)along internal passageways;involuntary control.

Location: Mostly in the walls ofhollow organs.

Photomicrograph: Sheet of smoothmuscle (720x).

Smoothmusclecell

Nuclei

Figure 4.9c Muscle tissues.

Nervous Tissue

• Main component of nervous system

• Brain, spinal cord, nerves– Regulates and controls body functions

• Neurons– Specialized nerve cells that generate and conduct nerve

impulses

• Neuroglia– Supporting cells that support, insulate, and protect neurons


Nervous tissue

Description: Neurons arebranching cells; cell processesthat may be quite long extend fromthe nucleus-containing cell body;also contributing to nervous tissueare nonexcitable supporting cells.

Function: Neurons transmitelectrical signals from sensoryreceptors and to effectors (musclesand glands) which control theiractivity; supporting cells supportand protect neurons.

Location: Brain, spinalcord, and nerves.

Photomicrograph: Neurons (350x).

Neuronprocesses

Nuclei ofsupportingcells

Cell bodyof a neuron

Neuron processes Cell body

Axon Dendrites

Figure 4.10 Nervous tissues.

Lining Membranes

• Composed of at least two primary tissue types– An epithelium bound to underlying connective

tissue proper

• Three types– Cutaneous membranes– Mucous membranes– Serous membranes– Synovial membrane (connective tissue only, Ch. 8)

Cutaneous Membrane

• Skin– Keratinized stratified squamous epithelium

(epidermis) attached to a thick layer of connective tissue (dermis)

• The only dry membrane

Mucous Membranes

• Epithelial sheet lies over layer of connective tissue called lamina propria

• Line body cavities open to the exterior– Digestive, respiratory, urogenital tracts

• Mucosa indicates location not cell composition– All called mucosae


Mucous membranes

Mucous membranes line bodycavities that are open to theexterior.

Mucosa ofnasal cavityMucosa ofmouthEsophagusliningMucosa oflung bronchi

Figure 4.11b Classes of membranes.

Serous Membranes

• Serosae—found in closed ventral body cavity

• Simple squamous epithelium (mesothelium) resting on thin areolar connective tissue

• Parietal serosae line internal body cavity walls• Visceral serosae cover internal organs

• Serous fluid between layers


Visceralperitoneum

Parietalperitoneum

Parietalpericardium

Visceralpericardium

Visceralpleura

Parietalpleura

Serous membranes line body cavities that are closed to the exterior.

Serous membranes

Figure 4.11c Classes of membranes.

Today’s Lab

• Lab Exercise 6

• Learn to identify tissue under the microscope and understand their general functions

anatomy & physiology i lecture 3 chapter 4: tissues

Documents

microscopy tissue

colon tissue

epithelial tissues

movement epithelial

layers of cells

lining epithelia

connective tissues

basic tissue types