Cell & Tissue

Rishi PokhrelMBBS, MD

MajAssistant prof of Anatomy

Classification• Somatic and germ cells

– Somatic cells are present in body structure and contain 46 pairs of chromosomes.

– Germ cells are formed for the purpose of reproduction and they are present only in testes or ovaries. They contain 26 pairs of chromosomes.

• On the basis of regeneration cells can be – Labile cells: cells undergoing continuous replication e.g. epithelium of skin

and mucosa, uterus, secretory glands, bone marrow, blood, spleen and lymphoid tissue.

– Stable cells: these cells undergo very slow or infrequent replication e.g. cells of liver, kidney and pancreas, fibroblasts, smooth muscle cells etc.

– Permanent cells: these cells do not divide after normal growth and development e.g. neurons, skeletal and cardiac muscle cells.

Composition

• water (70-80 %)• Proteins (10-20%)• Lipids (2%) and • Carbohydrates (1%).• Electrolytes like Sodium, Calcium, Chloride,

Potassium, magnesium, phosphate, sulfate and bicarbonate

Cell organells

• Cell membrane

Organelles

• Cytoplasm• Endoplasmic reticulum• Ribosomes• Mitochondria• Golgi bodies• Lysosomes• Nucleus• Centrioles

Nucleus

• Cytoskeleton• Cell junctions

– Tight junctions– Gap Junctions– Desmosomes

Tissue

• Epithelial tissue• Connective tissue• Muscular tissue• Nervous tissue

Epithelium

Glands

• “An organ in the body that secretes particular chemical substances for use in the body or for discharge into the surroundings”

• Epithelial cells are major components of glands

Classification• Duct system

– Endocrine

– Paracrine

– Exocrine• Simple

• Compound

– Mixed

• Means of secretion– Merocrine (Eccrine) – sweat, mammary– Apocrine – genitoanal glands– Holocrine – Sebaceous– Cells producing - Testis

Classification

• No of cells– Unicellular – goblet cells– Multicellular

• Type of secretion– Mucus– Serous

Classification

• Secretory component

– Tubular

– Acinar

– Coiled

– Branched

Classification

• Embryological origin– Ectodermal - sweat– Mesodermal – kidneys, testis– Endodermal - GI

Classification

Connective tissue

“Connective tissues (CT) are a group of

tissues which connects or binds other

tissues in the body”

CHARACTERISTICS

• Predominantly intercellular material (matrix)• Cells widely spaced• Development – mesoderm, neural crest

(head region)• Blood vessels – few supply• Classification – based on matrix, cells, fibres

Components

Cells Matrix

Ground substance Fibers

COMPOSITION: CONNECTIVE TISSUE

Composition

Components

Cells

Fixed

Fibroblasts

Adipocytes

Persistent mesenchymal

cells

Wandering

Macrophage

Mast cells

Plasma cells

Pigment cells

Eosinophil

Neutrophil

Matrix

Ground substance

Proteoglycans GAG /MPS

SO4

Non SO4

Fibers

Collagen

Elastic

Reticular

CONNECTIVE TISSUE

CELLS OF CONNECTIVE TISSUE

FIBRES

• COLLAGEN

• ELASTIC

• RETICULAR

Collagen

Ligament -TS

Ligament - LS

Elastic fibers

Reticular fibers

Collagen Elastic ReticularColor Pearly white Yellow -No Largest Next > In emb CTStain & appearance

Dull pink with eosin Bright, highly refractive

Not stained by H & E

Protein Collagen Elastin Reticulinthickness 1-12 um 0.1-0.2 um thinnestFeatures Wavy, do not branch, run

in bundles< wavy, branch, run singly

Straight, branch & anastomose-reticulum

Sites To provide strength; tendon, ligament etc.

To provide elasticity; lig nuche, vocal cords, lungs, aorta

To provide support; spleen, liver, lymph nodes, kidney, BM

GROUND SUBS

• Amorphous, transparent, semi-fluid gel

• Proteoglycans, hyaluronic acid (GAG), water

• Proteoglycans: chondroitin SO4, chondroitin

6 SO4, dermatan SO4, heparan SO4, heparin

SO4, keratan SO4

CLASSFICATION OF C. T.• Types of cells• Types of fibres• Amount of ground subs• Location

Connective tissue

Adult

Ordinary

Loose

Areolar

Adipose

Reticular

Dense

Regular

Tendon

Ligament

Aponeurosis

Irregular

Subcutaneous tissue

Specialized

Blood

Cartilage

Bone

Fetal

AREOLAR TISSUE

ADIPOSE TISSUE

TENDON L. S.

TENDON T. S.

BoneDefinition:

“Specialized connective tissue with a solid matrix which is mineralized & adapted for giving strength,

support & helping in wt. transmission”

Classification

General microstructure

• Non – lamellar bone / woven bone - immature

• Lamellar bone – mature

– Compact bone

– Spongy spongy

Bone

Cells

Osteoprogenator cells

Osteoblasts

Osteocytes

Bone lining cells

Osteoclasts

Matrix

Ground substance

Water

ProteoglycansChtn SO4, Hyal. Acid, osteocalcin, osteonection

Minerals Ca,Ca(OH)2(PO4)6

Fibers

Collagen

COMPOSITION

Osteoprogenitor /osteogenic cells

• From pluripotent stromal stem cells• Mesenchymal• Resemble young fibroblasts• In adults

• Deepest layer of periosteum• Endosteum

Osteoblasts• Resemble plasma cells• 15 – 30 µ • Roughly cuboidal• Nu eccentric• Cytoplasm deeply basophilic• EM – typical protein secreting cell• Function

– Synth & secretion of osteoid– Mineralization of matrix

Osteocytes

• Smaller & < basophillic• Major cell type• Oval, 25µ in long axis• Prominent nu• Cell in lacuna• Canaliculi 0.25 – 0.5µ

Osteoclasts

• Large cells

• 20 - 100µ

• Oval cells with multiple nu 15 – 20 or >

• Where active resorption

• Cells in pits – resorption bays/ lacunae of howship

Woven Bone / Non Lamellar Bone

• Most primitive form• Most bone – pre natal life• Post natal

• Repair of #• Rapidly growing bone tumors (osteogenic cells)

• Mechanically weak

Lamellar Bone/ Mature Bone

Haversian System

Bone Ground Section L.S.

Bone Ground Section T.S.

Periosteum• Outer covering• Absent

• Articular surface• Sesamoid bones

• Two layers• Outer fibrous • Inner cellular

• Sharpey’s fibres/ extrinsic fibres

Sharpey’s Fibres

Cartilage

• Specialized connective tissue for high resistance – tension, compression & shearing (Resilience & Elasticity)

• Avascular, no lymphatics, no nerve supply• Low metabolic rate

Constituents• Cells – chondrocytes, chondroblasts

– Located in lacunae

• Matrix

– Fibers: Collagen, elastic

– Ground substance: hyaluronic acid, proteoglycans, glycoproteins, chondroitin SO4

• Macromolecules, water & fibers bind together to give firm, flexible property

Perichondrium

• Dense CT that covers cartilage (except articular & fibrocartilage)

• Supplied by vessels & nerves

• Contains collagen fibers, fibroblasts

Types of Cartilage

• Hyaline– Costal– Articular

• Elastic• Fibro cartilage

Hyaline Cartilage

• Nose, trachea, larynx

• Bluish white color• Strong, rubbery &

flexible

Hyaline Cartilage

Elastic Cartilage

• Similar to hyaline • Fibers: collagen + elastic• Found in - auricle of ear, external auditory

canals, eustachian tubes, epiglottis• Maintains shape, deforms but returns to

shape; flexibility of organ; strengthens and supports structures.

Elastic Cartilage

Fibrocartilage• No Perichondrium

• Collagen fibres (Type I) – Densely packed bundles

– Feathery appearance

– Merge with surrounding CT

• Scanty Chondrocytes– Small cells in lacunae

– form short rows between dense bundles of collagen fibres

Identifying features

• Costal cartilage– Perichondrium +– Ground glass appearance– Cells ++

• Articular cartilage– Perichondrium –– Ground glass appearance– Cells +

• Elastic cartilage– Perichondrium +– Elastic fibers seen– Cells ++

• Fibrocartilage– Perichondrium –– Feathery appearance– Cells +

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