TissuesTissues

Chapter 4Chapter 4

TissueTissue - groups of cells with similar structure - groups of cells with similar structure and function. and function.

Four principle human tissue types: Four principle human tissue types:

epithelium (covering) epithelium (covering)

connective (support) connective (support)

muscle (movement) muscle (movement)

nervous (control) nervous (control)

Histology: study of tissuesHistology: study of tissues

A fertilized egg called a zygote will rapidly A fertilized egg called a zygote will rapidly divide into a blastocyst.divide into a blastocyst.

By week 3: three layered embryo (gastrulation)By week 3: three layered embryo (gastrulation)

- ectoderm: “outer skin”, epidermis and - ectoderm: “outer skin”, epidermis and nervous system nervous system

- mesoderm: skeletal, muscular and - mesoderm: skeletal, muscular and circulatory systems circulatory systems

- endoderm: “inner skin” linings of the - endoderm: “inner skin” linings of the digestive and digestive and respiratory respiratory tracts tracts

Epithelial: sheet of cells that covers body Epithelial: sheet of cells that covers body surfaces and lines inside of body surfaces and lines inside of body cavities. cavities.

Glandular epithelium: glandsGlandular epithelium: glandsFunctions:Functions:

- protection- protection- absorption- absorption- filtration- filtration- excretion- excretion- secretion- secretion- sensory reception- sensory reception- gas exchange- gas exchange

Characteristics of epithelial tissue:Characteristics of epithelial tissue:

- - CellularityCellularity: composed of closely packed cells: composed of closely packed cells

- - Specialized contactsSpecialized contacts: tight junctions and : tight junctions and desmosomes bind these closely packed cellsdesmosomes bind these closely packed cells

-- Polarity Polarity: apical surface:: apical surface:

- free surface exposed- free surface exposed

basal surface: basal surface:

- lower surface attachment- lower surface attachment

- - Basement membraneBasement membrane: basal lamina (filtering) + : basal lamina (filtering) + reticular lamina (collagen protein fibers).reticular lamina (collagen protein fibers).

Together they help resist tearing and stretching of Together they help resist tearing and stretching of epitheliumepithelium

- AvascularityAvascularity: epithelial tissue does not have a blood : epithelial tissue does not have a blood supply.supply.

- RegenerationRegeneration: replace lost tissue via cell division: replace lost tissue via cell division

Epithelium classification:Epithelium classification:All epithelial tissue has two names:All epithelial tissue has two names:11stst: number of cell layers: number of cell layers22ndnd: shape of cells: shape of cells

Number of cell layers:Number of cell layers:Simple: single layer (absorption and filtration)Simple: single layer (absorption and filtration)Stratified: multiple layers (protection)Stratified: multiple layers (protection)Pseudostratified: artificial/false layers Pseudostratified: artificial/false layers

Shape of cells:Shape of cells:Squamous: flat and scale likeSquamous: flat and scale likeCuboidal: cube shapedCuboidal: cube shapedColumnar: column shapedColumnar: column shapedTransitional: variesTransitional: varies

1) Simple Squamous Epithelium:1) Simple Squamous Epithelium:

a.       Description:  single layer of flattened cells a.       Description:  single layer of flattened cells with a disc-shaped central nuclei and sparse with a disc-shaped central nuclei and sparse cytoplasm.cytoplasm.

b.      Function:  allows passage of materials by b.      Function:  allows passage of materials by diffusion and filtration in sites where diffusion and filtration in sites where protection is not important. Also secretes protection is not important. Also secretes lubricant.lubricant.

c.       Locations:  Kidney glomeruli, air sacs of c.       Locations:  Kidney glomeruli, air sacs of lungs, capillaries, linings of heart and lungs, capillaries, linings of heart and lymphatic system.lymphatic system.

2)2) Simple cuboidal epithelium Simple cuboidal epithelium

a.       Description:  single layer of cube-like cells a.       Description:  single layer of cube-like cells with large spherical centrally located with large spherical centrally located

nuclei.nuclei.

b.      Function:  secretion and absorptionb.      Function:  secretion and absorption

c.       Locations:  Kidney tubules, ducts and c.       Locations:  Kidney tubules, ducts and secretory portions of glands, ovary surfacesecretory portions of glands, ovary surface

3)3)    Simple columnar epithelium    Simple columnar epithelium

a.       Description:  single layer of tall cells with a.       Description:  single layer of tall cells with round to oval nuclei; some cells bear round to oval nuclei; some cells bear

cilia; cilia; may contain goblet cells that may contain goblet cells that produce produce mucus.mucus.

b.      Function: absorption; secretion of mucus b.      Function: absorption; secretion of mucus and enzymes; cilia propel substances.and enzymes; cilia propel substances.

c.       Location:  non-ciliated type lines digestive c.       Location:  non-ciliated type lines digestive tract, gallbladder, and ducts from glands; tract, gallbladder, and ducts from glands; ciliated type lines small bronchi, uterine ciliated type lines small bronchi, uterine tubes, and uterus.tubes, and uterus.

4)4)    Pseudostratified columnar epithelium    Pseudostratified columnar epithelium

a.       Description: single layer of cells of a.       Description: single layer of cells of differing differing heights so that nuclei are a differing levels; heights so that nuclei are a differing levels;

may may contain goblet cells and bear cilia. All cells contain goblet cells and bear cilia. All cells contact the basement membrane but not the free contact the basement membrane but not the free surface (only the tallest cells). Nuclei are at surface (only the tallest cells). Nuclei are at different different levels giving the false appearancelevels giving the false appearance

b.      Function:  secretion, propulsion by ciliary b.      Function:  secretion, propulsion by ciliary action.action.

c.       Location:  non-ciliated type lines male c.       Location:  non-ciliated type lines male reproductive ducts; ciliated type lines much reproductive ducts; ciliated type lines much of of respiratory tract.respiratory tract.

5)5)   Stratified squamous epithelium   Stratified squamous epithelium

a.       Description: thick layers of flattened cells; a.       Description: thick layers of flattened cells; often keratinized layer and a mitotic often keratinized layer and a mitotic

layer.layer.

b.      Function:  protects underlying tissues in b.      Function:  protects underlying tissues in areas subject to abrasionareas subject to abrasion

c.       Location:  non-keratinized type lines the c.       Location:  non-keratinized type lines the mouth and vagina; keratinized type mouth and vagina; keratinized type

forms forms the epidermis of skin.the epidermis of skin.

6)6)   Transitional epithelium   Transitional epithelium

a.       Description:  resembles both stratified a.       Description:  resembles both stratified squamous and stratified cuboidal.  Basal squamous and stratified cuboidal.  Basal cells are cuboidal or columnar; surface cells are cuboidal or columnar; surface cells are dome shaped.cells are dome shaped.

b.      Function:  stretches readily and permits b.      Function:  stretches readily and permits distension.distension.

c.       Location:  Lines uterus, bladder, and c.       Location:  Lines uterus, bladder, and urethraurethra

7) 7)     Glandular epithelium    Glandular epitheliuma.       Endocrine glands: “ductless” glands that a.       Endocrine glands: “ductless” glands that

produce hormones.produce hormones.b.      Exocrine glands: glands possessing ducts b.      Exocrine glands: glands possessing ducts

                                                                                                                                                            

              Merocrine: secrete products by exocytosis.Merocrine: secrete products by exocytosis.pancreas and sweat glandspancreas and sweat glands

                                                                                                                                                                          Holocrine: accumulate products until the Holocrine: accumulate products until the

cell ruptures. Sebaceous “oil” cell ruptures. Sebaceous “oil” glandsglands

  

Connective tissue: most abundant tissue in Connective tissue: most abundant tissue in human body. human body.

- binding and support (ligaments)- binding and support (ligaments)

- protection (bone)- protection (bone)

- insulation (adipose)- insulation (adipose)

- transportation (blood)- transportation (blood)

- absorb shock- absorb shock

- immunity- immunity

Ground substance: unstructured material that Ground substance: unstructured material that fills the space between cells and contains the fills the space between cells and contains the fibers.fibers.

Classification of connective tissuesClassification of connective tissuesI- Embryonic connective tissueI- Embryonic connective tissue

- mesenchyme (all connective tissue - mesenchyme (all connective tissue derived)derived)

- mucous connective tissue (Wharton’s - mucous connective tissue (Wharton’s jelly found in fetus)jelly found in fetus)

II- Mature connective tissueII- Mature connective tissueA. Loose connective tissueA. Loose connective tissue

- areolar tissue- areolar tissue- adipose tissue- adipose tissue- reticular connective tissue- reticular connective tissue

B. Dense connective tissueB. Dense connective tissue- dense regular connective tissue- dense regular connective tissue- dense irregular connective tissue- dense irregular connective tissue- elastic connective tissue- elastic connective tissue

C. CartilageC. Cartilage- hyaline cartilage- hyaline cartilage- fibrocartilage- fibrocartilage- elastic cartilage- elastic cartilage

D. Bone (osseous) tissueD. Bone (osseous) tissueE. Blood (vascular) tissueE. Blood (vascular) tissue

Blast cells are active cells that secrete both fibers and Blast cells are active cells that secrete both fibers and ground substance (matrix). Cyte cells are mature ground substance (matrix). Cyte cells are mature cells that maintain (repair or regenerate) matrix. cells that maintain (repair or regenerate) matrix. Examples of connective tissue cell types are as Examples of connective tissue cell types are as follows: follows:

Connective tissue proper - fibroblasts/fibrocytes Connective tissue proper - fibroblasts/fibrocytes

Cartilage - chondroblast/chondrocyte Cartilage - chondroblast/chondrocyte

Blood - hemocytoblast/hemocyte Blood - hemocytoblast/hemocyte

- Hematopoietic stem cells: blood producing - Hematopoietic stem cells: blood producing cells cells

Bone - osteoblast/osteocyte Bone - osteoblast/osteocyte

Loose connective tissue- loosely woven fibersLoose connective tissue- loosely woven fibersAreolar: Most widely distributed connective Areolar: Most widely distributed connective

tissue in the bodytissue in the body- binds body parts- binds body parts- wraps around small blood vessels - wraps around small blood vessels and nerves. and nerves.- binds skin to underlying structures- binds skin to underlying structures- composed mainly of fibroblasts- composed mainly of fibroblasts- forms lamina propria in mucous - forms lamina propria in mucous membranes membranes

Adipose: primarily made of adipocytes. Adipose: primarily made of adipocytes.

- storage of triglycerides- storage of triglycerides

- nucleus is pushed to the side- nucleus is pushed to the side

- insulator- insulator

- reduces heat loss through skin.- reduces heat loss through skin.

- energy reserve- energy reserve

- subcutaneous, around kidneys, - subcutaneous, around kidneys, omentum (over intestines), behind omentum (over intestines), behind eyeball (orbital fat)eyeball (orbital fat)

OmentumOmentum

Reticular: composed of reticular fibersReticular: composed of reticular fibers

- forms stroma (internal framework) in - forms stroma (internal framework) in organs; mainly lymphoid organs; mainly lymphoid

- spleen- spleen

- lymph nodes- lymph nodes

- bone marrow- bone marrow

- supports white blood cells- supports white blood cells

- binds smooth muscle cells together.- binds smooth muscle cells together.

Dense regular connective tissueDense regular connective tissue

- fibrous connective tissue- fibrous connective tissue

- bundles of - bundles of collagen collagen fibers with fibroblastsfibers with fibroblasts

strongest and most abundant.strongest and most abundant.

- high tensile strength fibrous - high tensile strength fibrous proteinprotein

- collagen molecules are - collagen molecules are secreted in the extracellular secreted in the extracellular spaces and fibers are spaces and fibers are

spontaneously formed; spontaneously formed; called white fiberscalled white fibers

- tendons: muscle to bone- tendons: muscle to bone

- aponeuroses : sheet like tendons (muscles to - aponeuroses : sheet like tendons (muscles to other muscle/bones)other muscle/bones)

- ligaments : bone to bone. Contain more - ligaments : bone to bone. Contain more elastin fibers so they have a elastin fibers so they have a

better ability to stretch. better ability to stretch.

TendonTendon

Dense irregular connective tissue: contains Dense irregular connective tissue: contains collagen fibers that have an irregular pattern.collagen fibers that have an irregular pattern.

- seen in sheets- seen in sheets

- tensions are exerted in various - tensions are exerted in various directions directions

- dermis of skin- dermis of skin

- periosteum of bone- periosteum of bone

- heart valves- heart valves

Cartilage: ability to endure great stress.Cartilage: ability to endure great stress.

- contains dense network of collagen and - contains dense network of collagen and elastic fibers embedded in chondroitin elastic fibers embedded in chondroitin

sulfate.sulfate.

- chondrocytes are located in spaces - chondrocytes are located in spaces called called lacunae.lacunae.

- has no blood supply- has no blood supply

- no nerves- no nerves

Hyaline cartilage: called gristle. Most abundant Hyaline cartilage: called gristle. Most abundant type of cartilagetype of cartilage

- located: ends of long bones (articular - located: ends of long bones (articular cartilage) cartilage)

- nose- nose

- trachea- trachea

- bronchi- bronchi

- ends of ribs- ends of ribs

- flexibility- flexibility

- movement of joints- movement of joints

- support- support

Fibrocartilage: chondrocytes scattered among Fibrocartilage: chondrocytes scattered among collagen. collagen.

- pubic symphysis- pubic symphysis

- intervertebral discs- intervertebral discs

- menisci of the knee.- menisci of the knee.

- support and fusion- support and fusion

- absorb compressive shock- absorb compressive shock

Elastic cartilage: Similar to hyaline cartilage, Elastic cartilage: Similar to hyaline cartilage, more elastic fibers present (stretching)more elastic fibers present (stretching)

- pinna of ear- pinna of ear

- epiglottis- epiglottis

- vocal cords- vocal cords

- walls of artery- walls of artery

Bone (osseous) tissue: Support, protection, Bone (osseous) tissue: Support, protection, storage, blood forming tissues.storage, blood forming tissues.

- calcified matrix with many collagen fibers- calcified matrix with many collagen fibers

- lie in “little lakes” called lacunae.- lie in “little lakes” called lacunae.

- blood cell formation (hematopoiesis)- blood cell formation (hematopoiesis)

- well vascularized- well vascularized

- mature cells called osteocytes- mature cells called osteocytes

Muscle tissue:Muscle tissue:

1- 1- Skeletal muscle tissueSkeletal muscle tissue (striated): Long slender and (striated): Long slender and multinucleated; many mitochondria. Voluntary. multinucleated; many mitochondria. Voluntary. Attached to muscle (bone movers)Attached to muscle (bone movers)

2- 2- Smooth muscle tissueSmooth muscle tissue (no striations): central (no striations): central nucleus. Involuntary. Located in walls of hollow nucleus. Involuntary. Located in walls of hollow organs; GI tract, blood vessels.organs; GI tract, blood vessels.

3- 3- Cardiac muscle tissueCardiac muscle tissue (striated): heart muscle (striated): heart muscle (myocardium). Contains intercalated discs (electrical (myocardium). Contains intercalated discs (electrical connectors). Autorhythmicity. Involuntary controlconnectors). Autorhythmicity. Involuntary control

Skeletal MuscleSkeletal Muscle

Smooth MuscleSmooth Muscle

Cardiac MuscleCardiac Muscle

Nervous tissue: basic cell is neuron.Nervous tissue: basic cell is neuron.

- generate and conduct nerve impulses- generate and conduct nerve impulses

- brain, spinal cord and nerves- brain, spinal cord and nerves

- dendrites, cell body and axon- dendrites, cell body and axon

Blood (connective) tissue: Blood (connective) tissue:

- develops from mesenchyme- develops from mesenchyme

- soluble proteins in plasma will clot - soluble proteins in plasma will clot blood blood and from visible fibers and from visible fibers

- Transport gases, nutrients and waste - Transport gases, nutrients and waste products products