Tissues

Definitions

• Tissues are groups of cells that have the same structure and functions.

• The study of tissues is called HISTOLOGY– Histos: tissue; ology: field of study

Classification of tissues

• Epithelial– Simple (one layer)

• Squamous• Cuboidal• Cilindrical

– With microvilli or “brush border”.– Cilia

• Pseudostratified– Stratified (several layers)

• Squamous• Cuboidal• Cilindrical• Transition

Classification of Tissues

• Connective– Proper

• Mesenchyme• Loose connective

– Areolar– Reticular– Adipose

• Dense connective tissue– Dense regular– Dense irregular

– Cartilage• Hyaline• Elastic• Fibrocartilage

– Oseous– Blood

Classification of Tissues

• Muscular– Skeletal muscle– Cardiac muscle– Smooth muscle

• Nervous tissue

Epithelial tissue

• Characteristics– Polarity: posses apical surface and basal surface.– Cellularity and special contacts (tight junctions).– Supported by connective tissue through basement

membrane (basal lamina + reticular lamina).– Avascular: no blood vessels.– Regenerative: cells regenerate.

• Function: lining of surfaces (interior or exterior to the body)

Figure 3.5

Simple Epithelium

• Simple Squamous epithelium: – Description: “scale like” flat cells.– Function: Allows passage of substances

through filtration and diffusion. – Located in endothelium (lining of blood

vessels), kidney glomeruli, air sacs in the lung (alveoli).

Figure 4.1

Simple squamous

Figure 4.2

Simple Epithelium

• Simple cuboidal epithelium– Description: cells are of cubic form. – Function: secretion and absortion. – Located in kidney tubules, ovary surface

Figure 4.3

Simple Epithelium

• Simple Columnar (cilindrical) epithelium– Description: tall cells with round or oval nucleus. – Function: Absorption that can be increase by

cytoplasmatic projections of microvilli, secretion of mucus. If ciliated, it propels mucus by ciliary action.

– Located in digestive track, small intestine, uterus, lower respiratory system (bronchioles).

Figure 4.4

Figure 4.5

Simple Epithelium

• Pseudostratified columnar:– Description: single layer of cells, with

apparent different heghts due to the position of the nucleus.

– Function: secretion and propulsion of mucus.

– Located in the trachea.

Figure 4.6

Simple Epithelium

• Pseudostratified columnar– Description: appears to be stratified

squamous and cylindrical. – Function: allows stretching and containing

urine (avoiding leakage into adjacent tissues). – Found in the bladder.

Stratified Epithelium

• Stratified Squamous epithelium– Description: multilayer squamous cells. – Function: protection of underlying tissues. – Location: Non keratinized (thin skin) are found

in the esphagous, mouth,vagina. Keratinized (thick skin): palm and feet.

Figure 4.7

Stratified Epithelium

• Stratified Cuboidal epithelium– Description:bilayer of cuboidal cells. – Function: secretion. – Found in the ducts of glands such as

mammary, sweat and salivary.

Figure 4.8

Stratified Epithelium

• Stratified Columnar epithelium– Description: Several layers of cylindrical cells. – Function: secretion. – Found in the male urethra.

Figure 4.9

Stratified Epithelium

• Transitional epithelium– Description: Resembles both stratified

sqamous and stratified cuboidal epithelium; basal scells are cuboidal or cylindrical; surface cells are domed or squamous.

– Function: Allows distension and stretching. – Found in the lining of the urethers, bladder

and par of the urethra.

Figure 4.10

Connective Tissue Proper

• Areolar loose connective tissue

– Description: loose collagen reticular and elastic fibers, prescence of fibroblasts, macrophages, mast cells.

– Function: wraps provide nutrients and cushions organs.

– Found under epithelia, surrounds capillaries and packages organs, .

Connective Tissue

• Function: Support/connect tissues.• Description:

– Cells:• Fibroblast: most common.• Chondrocytes, ostoecytes: secrete respective extracellular matrix.• Myofibroblasts• Adipocytes

– Fibres• Collagen• Estastin• Reticulin

– Ground substance: amorphous transparent material.• Glucosaminoclycans (GAGs): Hyaluronic acid• Glycoproteins: fribrillin, fibronectin, integrin.

Figure 4.11

Connective Tissue Proper

• Reticular loose connective tissue– Description: predominant reticular fibers in a

network. – Function: Provides structure to lymph organs.– Located: Found in lymph organs (thymus,

lymph nodes).

Figure 4.13

Connective Tissue Proper

• Regular Dense connective tissue– Parallel arranged collagen fibers with

fibroblasts. – Function: Attaches muscles to bones or bones

to bones. Posses great tensile strength in one direction.

– Forms tendons, ligaments, aponeurosis.

Figure 4.15

Connective Tissue Proper

• Irregular Dense connective tissue– Description: Irregular arranged fibers with

fibroblasts. Forms the articulation capsules of organs and joints.

– Function: Posses great tensile strength in several directions.

– Location: reticular layer of the dermis, fibrous capsues of organs and joints.

Figure 4.14

Connective Tissue Proper

• Elastic Connective tissue– Description: Irregular arranged elastic fibers

with fibroblasts. Makes the tunica media in blood vessels.

– Function: Provides elasticity to the blood vessels.

– Location: Tunica media of arteries and veins.

Figure 4.16

Connective Tissue Proper

• Adipose loose connective tissue– Description: adipocytes embeded in scarce

areolar tissue.– Function: Energetic reserve, cushioning,

thermal insulation.– Location: Hypodermis, kidneys, abdomen,

breasts.

Figure 4.12

Cartilage

• Hyaline Cartilage:– Description: firm amorphous matrix

synthesized by chondroblasts. Mature matrix holds chondrocytes in lacunae.

– Function: Allows resilience, flexibility and compressibility to forces.

– Located: embryonic skeleton, joints, nose, trachea, ribs.

Figure 4.17

Cartilage

• Elastic cartilage:– Description: similar to hyaline, but a grater

ratio of elastic fibers.– Function: maintain structure while possesing

great flexibility.– Location: outer ear, epiglotis.

Figure 4.18

Cartilage

• Fibrocartilage:– Description:similar to hyaline but a greater

ratio of collagen fibers.– Function: posses high tensile strength but

maintaining compressibility.– Located: intervertebral discs, knee joint, pubic

symphisis.

Figure 4.19

Bone

• Compact bone– Description: Hard, calcified matrix.

Impereameable. Vascularized. Osteocytes in lacunae.

– Function: hematopoiesis (reb blood cell formation), storage of calcium and minerals. Composes the skeleton.

– Location: bones

Figure 4.20

Figure 4.21

Blood

• Description: red, white cells and fibrous proteins (firbinogen) in a fluid matrix (plasma)

• Function: transport of nutrients, wates, gases throughout the body.

• Located: within blood vessels.

Figure 4.22

Muscle

• Skeletal muscle– Description: long, cylindrical, multinucleated,

and striated.– Function: Voluntary movement; locomotion.– Located: skeleton

Figure 4.28

Figure 4.30

Muscle

• Cardiac Muscle– Description: branched, striated, uninucleated

cells, connected by cell juntions (intercalated discs)

– Function: propulsion of blood from the heart.– Location: heart.

Figure 4.31

Muscle

• Smooth muscle– Description: spindle shaped, uninucleated, no

striations.– Function: creates peristaltic movement in

digestive system and involuntary contraction of arrestor pili.

– Lacted: hollow organs, dermis

Figure 4.32

Nervous tissue

• Description: Composed mainly by neurons and support cells (glial cells).

• Function: transmit electrochemical signals to sense and control the body.

• Location. Brain, spinal cord, nerves.

Figure 4.33

Figure 4.35

Figure 4.37

Figure 4.38

• Note: to extra practice, you find an atlas in the lab book as well as a tutorial in the PhysioEx CD.