TissuesHistology- the study of tissue

Groups of cells that are similar in structure and perform a common or related function.

4 primary types:

Epithelial (covering)Connective (support)Muscle (movement)Nervous (control)

Epithelial-Used for covering (ex: organs) or Glands

Epithelial Function-protection, absorption, filtration, excretion, secretion, sensory reception

Characteristics of Epithelial:InnervatedAvascularHigh regenerative capacityPolar- Apical surface= free

Basal surface= attachedLots of cells / form sheets

2 names for epithelia:Layers: simple or stratifiedShapes: Squamous

Cuboidal Columnar

Simple Squamous- thin, permeable, for filtration or exchange, found in lungs, kidneys

2 types:Endothelium- inner covering, slick friction reducing lining vessels

Mesothelium- middle covering lining the ventral body cavity

Simple Cuboidal- secretion and absorption, found in glands

A gland consists of one or more cells that make and secrete a product

Endocrine gland- ductless, absorb and secrete product by diffusion (thyroid, adrenals, pituitary)

Exocrine gland- ducts (salivary, oil, liver, pancreas)

Simple Columnar- lines the digestive tract from stomach to rectum

Examples:

•Microvilli- lines intestine, absorbs nutrients

•Goblet Cells- secretes protective lubricating mucus

Stratified Squamous• Stratified Squamous- is most

widespread, thick, protective, is the external part of skin, covers tongue, lines mouth, throat, esophagus, anal canal, vagina

•Epidermis- the outer layer of the skin that contains a protective protein called keratin

•Stratified cuboidal and stratified columnar are rarer types (make up some ducts)

Connective Tissue

2 Parts

Cells (living)

• Fibroblast• Chondroblast• Osteoblast• Hemocytoblast

Matrix (non-living)

1) Ground Substance:• Amorphous material

2) Fibers:• Collagen• Elastin• Reticular

Mesenchyme (embryonic origin)

Fibroblast Chondroblast Osteoblast Hematoblast

Fibrocyte Chondrocyte Osteocyte Blood Cells

Connective Tissue Cartilage Bone BloodProper

Connective Tissue Proper

1) Loose Connective * Areolar * Adipose * Reticular2) Dense Connective * Regular * Irregular

Areolar (connective tissue proper)

• Gel like, wraps and cushions organs

Adipose (fat) connective tissue proper

• Matrix contains stored neutral fat oil• Shock absorber and insulator

Reticular Connective tissue proper

• Forms a soft internal skeleton (stroma)

• Found in lymphoid organs

Dense Regular connective tissue proper

• Parallel collagen fibers• Tendons, Ligaments

Dense Irregular connective tissue proper

• Thicker bundles of collagen fiber• Form sheets in body areas

where tension is exerted in different directions• Fibrous Joint Capsules, dermis

Cartilage

-Tough but flexible-Avascular-Devoid of nerves-80% water-Heals slowly

Cartilage-3 Types• 1) Hyaline Cartilage

• 2) Fibrocartilage

• 3) Elastic Cartilage

1) Hyaline Cartilage

• Embryonic skeleton• ends of long bone• costal cartilage (rib)• Nose• trachea, larynx• supports, reinforces• flexible

Fibrocartilage

Thick collagen fibers

Intervertebral Discs

Elastic Cartilage

•More elastin fibers

•Ear, Epiglottis

Bone•1) Compact bone

•2) Spongy bone

Bone• Hard calcified matrix

• Very well vascularized

• Gives support

Mesenchyme (embryonic origin)

Fibroblast Chondroblast Osteoblast Hematoblast

Fibrocyte Chondrocyte Osteocyte Blood Cells

Connective Tissue Cartilage Bone BloodProper

Blood•Various Complex Cells

Blood• Atypical Connective tiusse• Blood Cells= macrophages, wbc, rbc• Matrix= plasma• Fibers=soluable proteins that are

visible in clotting-Carries gas, nutrients, waste, etc.

Nervous Tissue

Makes up brain, spinal cord, nerves

• Neurons- highly specialized nerve cells generate and conduct nerve impulses• Supporting cells- no conducting,

support, insulate, and protect neurons

Muscle Tissue

•Highly vascular•Highly cellular•Function= movement

Skeletal Muscle Tissue• Voluntary• Attaches to bone, skin• Gross body movements• Long cylindrical, many nuclei• Striated (banded)

Skeletal Muscle Picture

Cardiac Muscle Tissue• Involuntary•Walls of the heart• Striated• Branched• Fit together by intercalated

discs

Cardiac Muscle Picture

Smooth Muscle TissueInvoluntaryFunction= to propel (squeeze) Found: in walls of hollow organs (uterus), digestive sys., urinary sys., blood

vesselsSpindle shapeCentral nucleusNO STRIATIONS

Smooth Muscle Picture

Functions of TissueProtection

•Mechanical protection= (barrier) skin, mucosa• Ciliary protection= epithelial

(trachea)• Chemical protection= glands

Inflammatory response

•Occurs when tissues are injured•Non-specific

Immune Response

• Specific• Takes longer to come to action• Involves antibodies

Tissue Repair•Three steps:–Inflammation–Organization–Regeneration

Inflammation

• Histamine macrophage, mast cell• Capillaries dilate• Leak clotting proteins• Clot scab

Organization

• Clot Granulation tissue• New blood vessels collagen

fibers scar

Regeneration• Epithelial cells migrate

across granulation tissue and thickens

The ability to regenerate:

• Good: Epithelial (skin, epidermis, mucosa)• Limited: Smooth muscle, dense

regular connective (ligaments, tendons)• Poor: Skeletal muscle, Cartilage