Unit II: OrganizationConnective & Epithelial

Chapter 4: 135-159

Chapter 6: 210

What is a tissue?• Group of similar cells and cell products that work together to perform

a specific structural or physiological role

What is a tissue?

• Arise from three primary germ layers:

Germ Layer Contributions to BodyEctoderm Integumentary system – epidermis; Nervous

system; Skeletal – hyoid and auditory ossicles; Endocrine – pituitary gland and adrenal medulla; Respiratory and Digestive systems – mucous epithelium of nose, mouth, and anus

Mesoderm Skeletal, Muscular, Cardiovascular, Lymphatic systems; Integumentary system – dermis and hypodermis; Endocrine – adrenal cortex; Urinary – kidneys; Reproductive – gonads

Endoderm Respiratory system; Digestive – including liver and pancreas; Urinary – except kidneys; Reproductive – except gonads; Endocrine – thymus and thyroid

What is a tissue?

• Tissues are composed of cells and matrix:

• Ground substance

• Fibers

• Most abundant

• Widely separated cells

• Connect organs to each other

• Functions:

• binding of organs

• support

• physical and immune protection

• movement

• storage

• heat production

• transport

Connective Tissue

Connective TissueMarfan Syndrome

• Inherited – dominant gene• Defective gene that would normally enable the body to

produce fibrillin• Symptoms:

• Tall and thin with disproportionately long appendages• Severe near-sightedness

• CAN AFFECT ANY PART OF THE BODY!• Heart: aorta, heart valves• Eyes: dislocation of lens, glaucoma, cataracts, detachment

of retina• Lung: breathing difficulties

• Treatment: only of the complications

Components:

• Cells:

• Fibroblasts – fixed, produce the matrix of the tissue

• Macrophages – large phagocytic cells that move

• Leukocytes – wander around looking for pathogens

• Plasma cells – synthesize antibodies

• Mast cells – secrete heparin and histamine

• Adipocytes – energy storage, insulation, cushioning/protection

Fibrous Connective Tissue

Fibrous Connective Tissue

Components:

• Fibers:

• Collagenous – tough, flexible, made of collagen

• Reticular – thin, branching collagen fibers, framework for certain organs

• Elastic – made of elastin; stretch and resume original shape

Fibrous Connective Tissue

Components:

• Ground Substance:

• Glycosaminoglycan (GAG) – regulation of water and electrolyte balance

• Proteoglycan – important in holding tissues together

• Adhesive glycoproteins – bind components within a tissue together

Fibrous Connective Tissue

Types:

• Loose and Dense Connective Tissue

Loose Connective Tissue

• Areolar

• Reticular

• Adipose

Dense Connective Tissue

• Dense regular

• Dense irregular

• Chondroblasts

• Supportive with a flexible rubbery matrix

•No blood vessels

• Uses diffusion to bring in nutrients and remove wastes

• Types:

• Hyaline

• Elastic

• Fibrocartilage

Cartilage - Connective Tissue

• An organ made of multiple tissues including osseous tissue which makes up most of the mass of the bones

• Osteoblasts

• Matrix – Calcium and collagen

• Types:

• Compact bone

• Spongy bone

Bone - Connective Tissue

Central canal

Osteon

Compact bone LM x 375

Osteocytes occupy lacunae that lie between the lamellae.

• Exposed to the environment or an internal space in the body

• Flat sheet of closely adhering cells

• No room for blood vessels

• Basement membrane – extremely thin layer of connective tissue between an epithelium and underlying tissue

• Apical surface

• Lumen

Epithelial Tissue

• Simple epithelium • Stratified epithelium

Epithelial TissueSimple vs Stratified

•Contains all types of cells and fibers

•Passageways for nerves and blood vessels (packing material)

•Underlies all epithelia, between muscles

Loose Connective TissueAreolar

• Loose network of reticular fibers and blood cells• Forms supportive framework for lymphatic organs• Found in lymph nodes, spleen, and bone marrow

Loose Connective TissueReticular

• Large empty-looking cells with thin margins; nucleus pressed against cell membrane

• Energy storage, insulation, cushioning• Deep to the skin and around kidneys and eyes• Well suited for function because – a. b.

Loose Connective TissueAdipose

• Densely, packed, parallel collagen fibers

• Stretched in one predicable direction

• Tendons and ligaments

Dense Connective TissueDense Regular

Collagenfiber

Fibroblastnuclei

Dense regular connective tissue in a tendon from the triceps muscle

LM x 440

• Densely packed, randomly arranged, collagen fibers and few visible cells

• Stretched in multiple directions• Deeper layer of skin, capsules around organs

Dense Connective TissueDense Irregular

Dense irregular connective tissue from the dermis

Collagenfiber

bundles

LM x 111

• Rubbery proteoglycan matrix; dispersed collagen fibers; clustered chondrocytes in lacunae

• Stiff but flexible, reduces friction

• Ends of bones at movable joints; sternal ends of ribs; supportive material in larynx, trachea, tip of nose, and fetal skeleton

Cartilage - Connective TissueHyaline

Hyaline cartilage from shoulder joint

Chondrocytesin lacunae

Matrix

LM x 500

• Hyaline cartilage with elastic fibers• Provides flexible, elastic support• External ear and epiglottis

Cartilage - Connective TissueElastic

• Hyaline cartilage with extensive collagen fibers

• Resists compression and absorbs shock

• Pubic symphysis, meniscus and intervertebral discs

Cartilage - Connective TissueFibrocartilage

Collagenfibers inmatrix

Chondrocytesin lacunae

Fibrous cartilage from intervertebral discLM x 400

• Calcified matrix in lamellae around a central canal• Osteocytes in lacunae between lamellae • Osteon– functional unit; canaliculi for exchange of

nutrients• Skeletal support; leverage for muscles; mineral storage

Bone - Connective TissueCompact

•Variety of cells and cell fragments: Non-nucleated or nucleated

• Plasma = ground substance, NO fibers!

• Transport cells and dissolved matter

• Found in heart and blood vessels

Blood - Connective Tissue

• Diffusion• Ex.: inner lining of heart and blood vessels, lungs,

kidneys

Epithelial TissueSimple Squamous

Nucleus Cytoplasm

LM x 270

View from top

• Dead layers packed with keratin– epidermis

• Retards water loss, barrier to organisms, resists abrasion

Keratinized

Epithelial TissueStratified Squamous

General function – resistance against abrasion/frictionTwo types:

Epithelial TissueStratified Squamous

• Lacks surface layers of dead cells

• Forms a moist, slippery layer, resists abrasion

• Ex.: Oral cavity, pharynx, esophagus, anus, vagina

Nonkeratinized

• Absorption and secretion, mucus production

• Lines glands

• Liver, thyroid, mammary and salivary glands, and kidney tubules

Epithelial TissueSimple Cuboidal

• Nuclei line up at basal surface, microvilli on apical surface• Absorption and secretion; mucus secretion • Inner lining of stomach, uterus, and kidney, intestine

Epithelial TissueSimple Columnar

• Not all cells reach apical surface, cilia

• Secretes and propels respiratory mucus

• Ex.: lining of nasal cavity, trachea, lungs, male reproductive tract

Epithelial TissuePseudostratified Columnar