Module 2: Epithelial, Connective, Bone and Cartilage Flashcards by Mary Rose Carvajal

Characteristics / Properties of Epithelial Cells

> Formed by epithelial cells
Extremely cohesive
Avascular
Provided with basement membrane

How well did you know this?

Not at all

Perfectly

Three germ layers of Epithelial Cells

Ectoderm
Endoderm
Mesoderm

How well did you know this?

Not at all

Perfectly

Surface covering and lines cavities

Epithelial Tissue

How well did you know this?

Not at all

Perfectly

Functions of Epithelial Tissue

Protection
Secretion
Absorption
Excretion
Sensory receptors
Filtration
Lubrication

How well did you know this?

Not at all

Perfectly

sheet-like arrangements of extra-cellular matrix proteins
Interface between support tissues and parenchyma
structural support

Basement membrane

How well did you know this?

Not at all

Perfectly

attachment of epithelial tissues
control of epithelial growth and differentiation*
permeable barrier
Type IV collagen
proteins: heparan SO4

Basement membrane

How well did you know this?

Not at all

Perfectly

Layers of Basal Lamina

Lamina lucida
Lamina densa
Lamina fibro-reticularis

How well did you know this?

Not at all

Perfectly

Components of Basal Lamina

Type IV ccollagen
Heparan SO4
Structural glycoprotein

How well did you know this?

Not at all

Perfectly

Structural glycoprotein

fibronectin
laminin
entactin

How well did you know this?

Not at all

Perfectly

Membrane Specializations:

Intercellular
Lumina
Basal

How well did you know this?

Not at all

Perfectly

Epithelial Tissue Membrane Specializations: Intercellular

Occluding junctions - tight, zonula occludens*
Adhering junctions* - zonula adherens, macula adherens
(desmosomes)
** junctional complex
Gap junctions / nexus

How well did you know this?

Not at all

Perfectly

Epithelial Tissue Membrane Specializations: Luminal

cilia – axoneme (microtubules)* , basal body
* doublets (complete (dynein), incomplete
microvilli - microfilaments (ZA), intermediate filaments(MA)
* striated / brush borders
stereocilia

How well did you know this?

Not at all

Perfectly

Epithelial Tissue Membrane Specializations: Basal

basement membrane - hemidesmosomes

How well did you know this?

Not at all

Perfectly

selective diffusion, absorption, secretion

- surface specializations (microvilli, cilia)

Simple Epithelium

How well did you know this?

Not at all

Perfectly

Simple epithelium
Layering of nuclei
Resting on basement membrane
In respiratory passages, male uro-genital tracts, female excretory ducts
Membrane specializations

Pseudostratified epithelium

How well did you know this?

Not at all

Perfectly

loose collagenous

- fibroblast , mast cells , macrophages

Papillary layer

How well did you know this?

Not at all

Perfectly

dense irregular c.t.
blood and lymph vessels
skin appendages

Reticular layer

How well did you know this?

Not at all

Perfectly

Basal - cuboidal
Intermediate - polygonal
Surface – rounded / flat
	1. large, pale, scalloped
	2 . thickened  
	3. ½ nuclei, large, round, prominent nucleoli

Transitional Epithelium

How well did you know this?

Not at all

Perfectly

Specialized to synthesize and secrete a specific product (Proteins, Lipids, CHO+CHON)

Glandular Epithelium

How well did you know this?

Not at all

Perfectly

Glandular Epithelium: Number of cells

Unicellular gland - Goblet cells- mucigen

2. Multicellular gland

How well did you know this?

Not at all

Perfectly

Glandular Epithelium: Manner of secretion

Endocrine – without ducts into blood / lymph
Exocrine – with ducts
Paracrine – paraneurons , into the ECS

How well did you know this?

Not at all

Perfectly

Glandular Epithelium: Mechanism for release or fate of cell after secretion

Merocrine – intact cell (Eccrine gland)
Apocrine – loss of part of the cell
Holocrine – total loss of the cell

How well did you know this?

Not at all

Perfectly

Glandular Epithelium: Nature or Characteristic or Type of secretion

Serous gland
Mucous gland
Mixed gland
Cytogenic gland

How well did you know this?

Not at all

Perfectly

Glandular Epithelium: Morphology or Structure:

Simple
a. simple tubular
b. simple coiled tubular
c. simple branched tubular
d. simple acinar ( alveolar )
e. simple branched alveolar
Compound
a. compound tubular
b. compound tubulo-alveolar
c. compound alveolar

How well did you know this?

Not at all

Perfectly

4 Fundamental Tissues

1. Epithelial 2. Connective 3. Muscular 4. Nervous

Functions of Connective Tissues

- Bind together, Support & Strengthen organs and soft tissues of the body - Protect and insulate internal organs - Repair of the body - Transport system, Hematopoiesis (blood) - Fat storage (adipose) - Immune response (white blood cells) - Protection against bacterial infection

Two Main Components of Connective Tissue

1. Extra cellular matrix - Consist of protein fiber and ground substance 2. Resident Cells -Fibroblast, Mesenchymal cells, Macrophage, Fat cells - Cells not usually touching each other - Lots of extracellular matrix - Well vascularized

are relatively few and widely separated. The intercellular substance is abundant, containing - a portion of tissue fluids - extracellular matrix ( protein fibers and ground substance)

Connective Tissue

Immature cells called

“-blasts”

Mature cells called

“-cytes”

Loose & dense CT

fibroblasts, fibrocytes

Cartilage

chondroblasts, chondrocytes

Bone

osteoblast, osteocytes

``` The character of _____ is determined from region to region by the abundance and proportion of Fluid Fibers Ground matrix molecule Mineral aggregates ```

Connective Tissue extracellular matrix

The embryonic origin of Connective Tissue develops from an embryonic tissue, the _____, which is characterized by branched cells embedded in an abundant amorphous intercellular substance.

mesenchyme

Embryonic Origin of Connective Tissue derived from the ___

Mesoderm

Connective Tissue can be categorized as:

1. Fixed cells = more or less permanent resident population e. g. Fibroblasts, mesenchymal cells, reticular cells, fat cells 2. Wandering = transient emigrants from the blood stream e. g. WBC, mast cells, plasma cells

- Principal cells of connective tissue - Responsible for the synthesis of fibers and ground matrix (glycosaminoglycans) - Derived from mesenchymal cells

Fibroblast

- Contain abundant and irregularly branched cytoplasm - The cytoplasm is basophilic due to the RER and Golgi complex - Its nucleus is ovoid, large and pale staining, with fine chromatin and a prominent nucleolus

Young Fibroblast

- Mature fibroblast (quiescent) - Tends to be spindle-shaped and has processes - Its nucleus is darker and elongated - Its cytoplasm is acidophilic - Mature fibroblast can be stellate shaped with multiple processes

Fibrocyte

- Also known as multipotential or pluripotential cells because of their ability to become transformed into other types of cells - Similar but smaller than fibroblasts - Flattened or stellate shaped

Mesenchymal Cells

- Also known as histiocytes - Monocular cells of varying appearance, with the ability to take particulate materials with their cytoplasm and degrade the ingested substance with hydrolytic enzymes by phagocytosis

Macrophages

- Derived mainly from precursor cells from the bone marrow that divide, producing monocytes - These cells circulate in the blood and then migrate to the connective tissue

Macrophages

Tissue macrophages can proliferate locally, which are present in practically all organs, constituting a diffuse system called

“Mononuclear – phagocytic system”

Precursor of Macrophages

Monocyte

Production of Cytokines, chemotactic factors, several molecules that participate in Inflammation (defense), antigen processing and presentation

Macrophage

Antigen processing and presentation in the epidermis of the skin

Langerhans Cell

Localized digestion of Bone matrix

Osteoclast (from fusion of several macrophages)

Antigen processing and presentation in the lymph nodes and spleen

Dendritic Cell

Production of Cytokines, chemotactic factors, several molecules that participate in Inflammation (defense), antigen processing and presentation in the Liver (perisinusoidal)

Kuppfer Cell

Production of Cytokines, chemotactic factors, several molecules that participate in Inflammation (defense), antigen processing and presentation in the CNS

Microglial Cell

Segregation and digestion of foreign bodies in connective tissue under various pathological conditions

Multinuclear Giant Cell (several fused Macrophages)

- Also known as adipocytes - Connective tissue cells that have become specialized for storage of neutral fats or heat production - Found singly or in groups, widely distributed in loose connective tissue

Fat Cells

- Accumulate lipid globules to such an extent that the nucleus is flattened and displaced to one side with a rim of cytoplasm around, giving a “signet” ring appearance - Large, oval or spherical shaped cells whose cytoplasm is displaced to the peripheral region of the cell by the presence of a single large fat droplet

Fat Cell

- Few or rare in connective tissue in most areas of the body - Numerous in sites subject to penetration of bacteria and foreign proteins and in areas where there is chronic inflammation

Plasma Cells

Some of plasma cells contain unusually large masses of electron dense materials and these are called ____ which probably represent the abberent state of the cells or represent degenerative changes in the cells

“Russell bodies”

Responsible for the synthesis of the antibodies found in the blood stream

Plasma Cells

Precursor of the plasma cell is the

B-lymphocyte

- Characterized as a large ovoid cell whose cytoplasm is filled with abundant intensely basophilic staining granules - The nucleus is spherical and centrally located; obscured by the cytoplasmic granules (basophilic secretory)

Mast Cell

are actively involved in anaphylactic reactions

Mast Cells

Mast cell's granules contain:

``` Heparin = anticoagulant Histamine = increases vascular permeability Serotonin = produces vasoconstriction and contraction of the smooth muscle ```

- Enter connective tissue from blood vessels as the “first wave” in acute inflammatory responses - Small cells with multi-lobed, heterochromatic nuclei (aka “polymorphonuclear neutrophils”, “PMNs”, “polys”)

Neutrophils

Primary function: anti-bacterial (are phagocytic like macrophages, but SHORT-lived and NOT antigen presenting)

Neutrophils

Extracellular fibers and Ground substance

Fibroblast (fibrocytes)

Antibodies

Plasma Cells

Various immune/defense functions

Lymphocytes

Modulate allergic/vasoactive reactions and defense against parasites

Eosinophilic Leukocytes

Phagocytosis of Bacteria

Neutrophilic Leukocytes

Phagocytosis of ECM components and debris; antigen processing and presentation to immune cells;secretion of growth factors,cytokinines and other agents

Macrophages

Pharmacologically active molecules(eg. Histamine)

Mast Cells and Basophilic Leukocytes

Storage of Neutral fats

Adipocytes

Connective Tissue Fibers

Collagen fibers Elastic fibers Reticular fibers

- Most numerous fibers in connective tissue - Fresh collagen fibers are colorless, but when present in great number, they cause the tissue in which they lie to be “white”, (e.g. tendons and aponeurosis)

Collagen Fibers

- They are about 0.5 to 2 um in diameter and of indefinite length - They run in all directions and if not under tension, they tend to have a slightly wavy course - Due to the oriented disposition of the elongated tropocollagen fibers, these structures are birefringent

Collagen Fibers

- are elastic and because of their molecular configuration, have greater strength When___ is denatured by boiling, it yields the familiar substance, gelatin

Collagen Fibers

- Seen in the light microscope, collagen fibers are acidophilic - They stain pink with eosin - is the most abundant protein of the human body presenting 30% of its dry weight

Collagen Fibers

Collagen Types

1. Fibril-Forming Collagens 2. Sheet-Forming Collagens 3. Linking/Anchoring Collagens

- Fibril-forming Collagen that is for Resistance to TENSION | - found in Skin(dermis), Tendon, Bone, Dentine, fascia, sclera, organ capsule, fibrous cartilage

Type I

- Fibril-forming Collagen that is for Resistance to PRESSURE | - found in Cartilage(Hyaline and Elastic), Vitreous Body

Type II

- Fibril-forming Collagen that is for structural maintenance in expansible organs - found in Skin, Muscle(smooth), Blood vessels(arterioles), endo-mesium, arterioles, uterus, liver, spleen, kidney, lungs, frequently together with type I

Type III

- Participates in Type I collagen function | - found in Fetal Tissues, Skin, Bone, Placenta, most Interstitial tissues

Type V

- Participates in Type II collagen function | - found in Cartilage

Type XI

- Type of Sheet-forming Collagen that is for Support of Epithelial cells, Filtration - found in All Basal and external laminae (epithelial, endothelial basal lamina)

Type IV

- Type of Linking/Anchoring Collagen that Anchors basal laminae to underlying reticular lamina - found in Epithelial Basement Membrane

Type VII

- Type of Linking/Anchoring Collagen that binds various proteoglycans; associated with Type II collagen - found in Cartilage, Vitreous body

Type IX

- Type of Linking/Anchoring Collagen that Interacts with Type I collagen - found in Placenta, Skin, Tendons

Type XII

- Type of Linking/Anchoring Collagen that Binds Type I collagen fibrils, with Types V and XII, strengthening fiber formation - found in Placenta , Bone

Type XIV

Type I collagen disorder which results to spontaneous fractures, progressive hearing loss, cardiac insufficiency

Osteogenesis imperfecta

Type III collagen disorder which causes hypermobility of digits, early morbidity/mortality from rupture of aorta or intestine

Ehlers-Danlos (type IV)

It is a multiple collagen disorder which causes ulceration of gums, hemorrhages

Scurvy (lack of vit. C, a cofactor for prolyl and lysyl hydroxylase)

- Imparts a yellowish color to the fresh tissue because of the presence of protein called elastin - They can be stretched by a small force and to return to their original dimensions when the force is removed

Elastic Fibers

- Resistant to boiling and hydrolysis by dilute acid or alkali – conditions that destroy other connective tissue constituents - Resists digestion by trypsin but when treated with the enzyme elastase, it is selectively digested from tissue secretion

Elastic Fibers

- Form a delicate supporting framework for highly cellular tissues (endocrine glands, lymph nodes, liver, bone marrow, spleen, smooth muscle). - Composed mainly of Type III collagen, with a carbohydrate moiety that reduces Ag+ to metallic sliver = argyrophilic. - Special stain: silver impregnation to visualize. - Thinner than type I collagen

Reticular (Reticulin) Fibers

-made by reticular cells (specialized fibroblasts) and vascular smooth muscle cells

Reticular Fibers (type III collagen)

are found in the stroma of many glandular organs, they are found in basal lamina of most epithelia and they form the supporting tissue of lymphoid and blood forming organs

Reticular Fibers

- The cells and fibers of connective tissue are surrounded by a translucent matrix that exhibits no structural organization visible with light microscope. - It is commonly referred to as “ground substance”

Extracellular / Ground Matrix

They contain acid principally mucopolysaccharide or glycosaminoglycans such as hyaluronic acid, chondroitun sulfate, dermatan sulfate, kerratin sulfate and heparin sulfate

Extracellular / Ground Matrix

Ground Substance of the Extracellular Matrix (ECM)

1. Glycosaminoglycans (GAG) 2. Proteoglycans 3. Multiadhesive glycoproteins

- linear (unbranched) polysaccharides, e.g. heparan sulfate, condroitin sulfate, keratan sulfate, hyaluronic acid - very hydrophilic due to abundant negative charges (e.g. SO4- groups). - except for hyaluronic acid, are usually bound covalently to protein core as part of a proteoglycan

Glycosaminoglycans (GAG)

- core protein + GAG side chains (like a bottle brush) | - bind cells, other proteins, and/or ECM components

Proteoglycans

- small glycosylated proteins containing NUMEROUS binding sites to cells, signaling molecules, and other ECM components - e.g. fibronectin and laminin: important for adhesion of epithelial cells to the basal lamina via transmembrane integrin receptors.

Multiadhesive glycoproteins

Classification Of Connective Tissues

1. Connective Tissue Proper 2. Embryonic Connective Tissue 3. Specialized Connective Tissue

Types of Connective Tissue Proper

Loose ( Areolar ) Ct Dense Irregular Ct Dense Regular Ct

Types of Embryonic Connective Tissue

Mesenchyme | Mucoid ( Mucous ) Ct

Type of Specialized Connective Tissue

``` Reticular Ct Adipose Tissue Cartilage Bone Blood ```

Fibrous Connective Tissued epending on the type of fiber that predominates, this is further subdivided into:

Collagenous connective tissue Elastic tissue Reticular tissue

Collagenous fibers predominate

Collagenous connective tissue

Classification of Collagenous Connective Tissue

Loose connective tissue Dense connective tissue Dense irregular connective tissue Dense regular connective tissue

- Widely distributed in the human body - Forms the superficial fascia and forms part of the framework or stroma of most of the organs - Surrounds blood vessels and nerves and fills otherwise unoccupied space

Loose Connective Tissue

- Composed of collagen fibers which are relatively few, far apart and runs in many directions - Contains potential spaces which are responsible for the term “areolar tissue” – a common synonym - delicate, vascularized, flexible; facilitates transport of cells and materials (secretion, absorption, immunity)

Loose Connective Tissue

This type of tissue is found in the - papillary layer of the dermis, - in the hypodermis of skin, - in the serosal linings of peritoneal and pleural cavities, - the pia mater of the spinal cord, - endoneurium and endomysium

Loose Connective Tissue

- Chiefly characterized by the close packing of its fibers | - These collagenous fibers occur in the form of bands, sheets, cords or bundles

Dense Connective Tissue

Subclassifications of Dense Connective Tissue

Dense irregular connective tissue | Dense regular connective tissue

- Composed of collagenous fibers arranged in bundles but are randomly oriented or runs in a few directions - Found in the dermis of skin, in the submucosa of the esophagus, in the capsule of organs, in periosteum and perichondrium

Dense irregular connective tissue

Densely packed collagen fibers, often in perpendicular bundles; resists tension in many directions and provides mechanical support.

Dense irregular connective tissue

- Occurs in cordlike structures and as bands - The collagenous fibers are usually in bundles that are oriented parallel to one another or arranged in one direction, giving a great tensile strength - Seen in tendons, ligaments, aponeurosis and fascia

Dense regular connective tissue

Found in: - Wall of hollow organs - Large artery (tunica media of aorta) - Internal elastic membrane of medium sized artery - Trachea, Bronchi, Vocal cords - Yellow ligaments of the vertebral column - Suspensory ligament of the penis

Elastic Tissue

- Reticular fibers predominate - Forms the supporting framework of the bone marrow and most of lymphoid and hematopoietic organs - Also found in close association with the basal lamina of most epithelia

Reticular Tissue

- Characterized by the presence of a mesenchymally derived cellular reticulum and fine extracellular fibrils - These fine slender fibrils are called the reticular fibers and the cells are reticular cells - The reticular fibers have a special staining affinity to silver salts, hence they are called “argyrophilic fibers”

Reticular Tissue

- Special type of connective tissue in which adipose cells predominate - Fat cells are found isolated in all loose connective tissue, but in certain places they are present in such large numbers and have such organization, to justify the designation of adipose tissue

Adipose Tissue

Principal Functions of Adipose Tissue

1. Storage of fat 2. Insulation against heat loss 3. Mechanical support in certain body regions

2 Types of Adipose Tissue

1. Yellow or white adipose tissue | 2. Brown adipose tissue

- Common adipose tissue - Comprises the bulk of the body - Adult or mature form of adipose tissue whose color ranges from white to dark yellow

Yellow or white adipose tissue

- The fat cell contains a single large fat droplet in the cytoplasm; it is unilocular in morphology - Found in subcutaneous tissue of skin, omentum, mesenteries and retroperitoneal fat

Yellow or white adipose tissue

- Fetal fat or immature form of adipose tissue - Its color ranges from tan to reddish brown - Its cell contains multiple lipid droplets in the cytoplasm; hence it is multilocular in morphology - Found in the interscapular and inguinal regions of newborns

Brown Adipose Tissue

- Present in newborns and hibernating mammals | - Involved in Thermoregulation

Brown (Multilocular) Adipose Tissue

- Mesenchymal cells predominate - Mesenchymal cells in the adults can be found in some parts of the uterus and fallopian tube, and especially along the course of blood vessels as in capillaries

Undifferentiated Mesenchymal Tissue

Mesenchymal cells are ____ because of their ability to transform to other types of tissues

multipotential (pluripotential)

- has an abundance of ground matrix composed chiefly of hyaluronic acid - Jelly-like tissue containing collagen fibers and a few elastic or reticular fibers

Mucous Connective Tissue

- Made up chiefly of large stellate fibroblast cells whose processes often are in contact with neighboring cells forming a network - A few macrophages and lymphoid wandering cells are also present

Mucous Connective Tissue

- The intercellular substance is very abundant, soft, jelly-like and homogenous in fresh specimen - The classic example is Wharton’s jelly of the umbilical cord - It is also found in the pulp of young teeth

Mucous Connective Tissue

- is a specialized form of firm and resilient connective tissue that can bear stresses without permanent distortion. - It consists of cells (chondroblasts, chondrocytes) and extracellular matrix, consisting of fibers and ground substance (hyaluronan, proteoglycans, glycoproteins).

Cartilage

- It is an avascular tissue. | - It serves as a precursor or model for the embryonic development and subsequent growth of many long bones

Cartilage

Types of Cartilage

1. Hyaline cartilage (Type II collagen) 2. Elastic cartilage (Type II collagen, elastic fibers) 3. Fibrocartilage (Type II and Type I collagen)

-It has a homogeneous amorphous matrix Collagen molecules (type II collagen fibrils), Proteoglycans (hyaluronan, chondroitin sulfate, keratan sulfate and AGGRECAN) and multiadhesive glycoproteins (noncollagenous and nonproteoglycan-linked glycoproteins) -Chondrocytes produce and maintain cellular matrix, and secrete metalloproteinases (enzymes that degrade cartilage matrix)

Hyaline Cartilage

Components of the hyaline cartilage (matrix are not uniformly distributed)

1. Capsular (pericellular) matrix –located immediately around the chondrocyte 2. Territorial matrix - it surrounds the isogenous group 3. Interterritorial matrix – is a region that surrounds the territorial matrix and occupies the space between groups of chondrocytes

True or False Perichondrium surrounds the hyaline cartilage; DICT, growth and maintenance of cartilage, blood supply

True

True or False Hyaline cartilage of articular joint surfaces do not possess a perichondrium

True

Components of Cartilage Matrix

1. Collagen Molecules - (Type II collagen) 2. Proteoglycans (3.5X106 daltons) - Glycosaminoglycans (GAGs) - Chondroitin sulfate, Keratin sulfate, hyaluronan - Aggrecan - Proetin Core 3. Multiadhesive glycoproteins (non collagenous and non proteoglycan-llinked glycoproteins, CHONDRONECTIN)

4 Zones of Articular Cartilage

Divided into four (4) zones: 1. Superficial (tangential) layer - Elongated and flattened chondrocytes surrounded by a condensation of collagen II 2. Intermediate (transitional )zone - Round chondrocytes randomly distributed 3. Deep (radial) zone - Small , round chondrocytes, in short columns perpendicularly arranged 4. Calcified zone - Small chondrocytes; calcified matrix

- Covers the surface of the ends of bones - It acts as a shock-absorber - There is no perichondrium - It enable the bones in the joints to move and glide over each other without friction - Avascular (lacking blood supply) *synovial fluid - Can get damaged due to the normal wear and tear that occurs with age or an injury

Articular Cartilage

degeneration of the cartilage in old age

Osteoarthritis

- Is distinguished by the presence of elastin in the cartilage matrix - The elastic material gives the cartilage elastic properties - It is surrounded by a perichondrium

Elastic Cartilage

- Matrix of elastic cartilage do not calcify during aging process - Found in external ear, external acoustic meatus, eustachian tube, epiglottis

Elastic Cartilage

- The toughest type of cartilage - referred to as WHITE CARTILAGE - It has the ability to withstand heavy weights.

Fibrocartilage

- It contains fine collagen fibers scattered in rows or layers (hyaline cart. + DCT) - With gaps between the lacunae and the bundles of collagen fibers - The number of chondrocytes is quite less, and the cells are embedded in the matrix material between the fibers, and not on the fibers

Fibrocartilage

- Contains both type I and type II collagen. - Very effective as a shock-absorber due to its ability to resist compression forces. - It provides support to the surrounding structures that are attached to it - It is found at the following places in the human body: In the intervertebral discs in the spine, Menisci in the knees, Pubic symphysis, where the hip bones join at the front of the body

Fibrocartilage

- Is a combination of a dense connective tissue and hyaline cartilage - Chondrocytes are dispersed singly , in rows, and in isogenous groups - No perichondrium

Fibrocartilage

Types of Cartilage Growth

1. Appositional Growth: Deposition of new cartilage on the surface of existing cartilage. 2. Interstitial Growth: Formation of new cartilage within an existing cartilage

- Provides support for the soft tissues of the body. - Provides sites for attachment of the muscles and tendons essential for locomotion. - Protects the vital organs of the cranium and various body cavities. - Encloses blood-forming elements in the bone marrow. - Plays an important role as a mobilizable store of calcium and phosphate

Bones

- Is a connective tissue characterized by a mineralized extracellular matrix - Mineral component is - Calcium phosphate hydroxy apatite crystals [Ca₁₀(Po₄)₆(HO)₂] - Storage site for calcium and phosphate (can be mobilized from the matrix and taken up by the blood (homeostatic regulation of calcium level)

Bones

For attachment of bone cells and collagen fibers to the mineralized ground substance

Multiadhesive glycoproteins

Multiadhesive glycoproteins of the Bone

1. Glycoproteins Osteonectin –serves as glue between the collagen and hydroxyappatite crystals 2. Sialoproteins Osteopontin –mediates attachments of cells to bone matrix Sialoprotein I and II –mediate cell attachment and initiate calcium phosphate formation during the mineralization process

Bone-specific, vitamin K-dependent proteins

1. Osteocalcin- captures calcium from the circulation and attracts and stimulates osteoclasts in bone remodelling 2. Protein S – assists the removal of cells undergoing apoptosis 3. Matrix Gla-protein (MGP)- participates in the development of vascular calcifications

also known as osteogenic protein -1 (OP-1) is now used clinically to induce bone growth after bone surgery (large bone defects, spinal fusions, implantation of grafts)

BMP-7

What are the different bone cells?

1. Osteocytes - Osteoprogenitor cells 2. Osteoblasts - Bone lining cells 3. Osteoclasts

- cortical bone - Dense bone in which the bony matrix is solidly filled with organic ground substance and inorganic salts, leaving only tiny spaces (lacunae) that contain the osteocytes or bone cells - makes up 80 percent of the human skeleton - forms a shell around cancellous bone and is the primary component of the long bones of the arm and leg and other bones

Compact Bone

- Cancellous bone or trabecular bone | - is highly vascular and frequently contains red bone marrow where hematopoiesis occurs

Spongy Bone

What are the different bone cavities?

1. Endosteal cells (osteoblastics and bone-lining cells) - flattened in shape with elongated nuclei and indistinguishable cytoplasmic features - Difficult to distinguish at the microscopic level 2. Red Bone Marrow- consists of blood cells of different stages of development and a network of reticular cells and fibers that serve as a supporting framework for the developing blood cells and vessels 3. Yellow Bone Marrow – fat cells

Zone in developing bone where it consists of hyaline cartilage with typical chondrocytes

Resting Zone

Zone in developing bone where chondrocytes begin to divide rapidly and form columns of stacked cells parallel to the long axis of bone

Proliferative Zone

Zone in developing bone where it contains swollen chondrocytes whose cytoplasm has accumulated glycogen and also hypertrophy compresses the matrix into thin septa between the chondrocytes

Hypertrophic Zone

Zone in developing bone where it has loss of the chondrocytes by apoptosis is accompanied by calcification of the septa of the cartilage matrix by the formation of hydroxyappatite crystals

Calcified Cartilage Zone

Zone in developing bone where bone tissue first appears; Capillaries and osteoprogenitor cells originating from the periosteum invade the cavities left by the chondrocytes; Osteoblast deposit osteoid over the spicules of calcified cartilage matrix, forming woven bone

Ossification Zone

process of bone formation

Osteogenesis (ossification)

- “within membrane”; in which osteoblasts differentiate directly from mesenchyme and begin secreting osteoid eg. Skull, clavicle

intramembranous ossification

- “within cartilage”; preexisting matrix of hyaline cartilage is eroded and invaded by osteoblasts which then begin osteoid production

endochondral ossification

- Consists of dense fibrous outer layer of collagen bundles and fibroblasts - The inner most cellular layer of periosteum contains mesenchymal stem cells (osteoprogenitor cells)

Periosteum

are bundle of periosteal collagen fibers penetrating the bone matrix (binding the periosteum to bone)

Perforating (or Sharpey’s fibers)

- Is a single very thin layer of connective tissues, containing flattened osteoprogenitor cells and osteoblasts, which covers the small spicules or trabeculae of bone that project into these cavities - Thinner than the periosteum

Endosteum

Principal functions of periosteum and endosteum

1. nutrition of osseous tissue | 2. provision of a continuous supply of new osteoblasts for repair or growth of bone

- Complex of concentric lamellae surrounding a small central canal contg. BV’s,nerves,LCT, and endosteum - VOLKMANN CANALS ( Per- forating canals) -transverse - CENTRAL CANAL -vertical

Haversian Canal and Haversian System (OSTEON)

- It is a flat, almond-shaped - Exhibit a significantly reduced RER and Golgi apparatus and more condensed nuclear chromatin - Is the mature bone cell (occupies each lacuna) - It is involved in maintaining the bony matrix, its death is followed by resorption of the matrix

Osteocytes

- Active phase (Cuboidal or polygonal to columnar shape, markedly basophilic cytoplasm - Non active phase (flatten with reduced cytoplasmic basophilia)

Osteoblasts

Osteoblast is a differentiated bone forming cells that secrete type I collagen and bone matrix proteins called ____

Osteiod

- Are very large, motile cells with multiple nuclei - Are mutinucleated cells found in resorption cavities (HOWSHIP LACUNAE) - Are derived from the fusion of mononuclear hemopoietic progenitor cells (GMP, CFU-GM) that give rise to granulocyte and monocyte cell linkage

Osteoclasts

Phagocytic action of Osteoclast is regulated by

PTH (Parathyroid Hormone) – promotes bone resorption | Calcitonin – reduces osteoclast activity

A ____ is a system of microtubule that osteocytes retain communication with the surface and with other cells

canaliculi

Two control loops regulate bone remodelling

- Hormonal mechanism maintains calcium homeostasis in the blood (negative feedback) - Mechanical and gravitational forces acting on the skeleton

- also known as Immature bone, Primary bone, Bundle bone - Irregular and random arrangement of cells and collagen; lightly calcified - found in developing and growing bones; hard callus of bone fractures

Woven Bone

- Mature bone; Secondary bone - Parallel bundles of collagen in thin layers (lamellae), with regularly spaced cells between; heavily calcified - found in all normal regions of adult bones

Lamellar Bone

- Cortical bone - Parallel lamellae or densely packed osteons, with interstitial lamellae - found in thick, outer region ( beneath periosteum) of bones

Compact Bone

- Spongy bone; Trabecular bone; Medullary bone - Interconnected thin spicules or trabeculae covered by endosteum - found in inner region of bones, adjacent to marrow cavities

Cancellous Bone

Ground substance of the Bone

- Osteonectin: anchor collagen to bone mineral - Osteocalcin: Calcium binding protein involved in bone calcification - Osteopontin: Binding of osteoblasts and osteoclasts to bone.

Cells responsible for the organs specialized function

Parenchyma

Cells which have supporting role in the organ

Stroma

Connective tissue that underlies the epithelial liming of organs

Lamina propia

Area between epithelium and connective tissue

Papillae

Electron dense layer consisting of network of fine fibrils

Basal lamina

Large glycoprotein that self assemble as lacelike network immediately below the basal pole

Laminin

a glycoprotein that initiates the development of basement membrane, cell extracellular matrix interactions and development of epithelium

Laminin

backbone of Zonule Occludens strands; from aqueous channels

Claudin

Calcium dependent (actin), for growth and differentiation

Cadherins

In communicating junction 1 connection is ____ connexin

Endochondral Ossification

1. Formation of Bone Collar 2. Cavitation of the hyaline cartilage 3. Invasion of Internal cavities by the peristyle 4. Formation of medullary cavity

Mechanism of bone repair

1. Hematoma formation 2. Fibrocartilaginous Callus formation 3. Bony callus formation 4. Bone remodelling