Module 2: Epithelial, Connective, Bone and Cartilage Flashcards
Characteristics / Properties of Epithelial Cells
> Formed by epithelial cells
Extremely cohesive
Avascular
Provided with basement membrane
Three germ layers of Epithelial Cells
- Ectoderm
- Endoderm
- Mesoderm
Surface covering and lines cavities
Epithelial Tissue
Functions of Epithelial Tissue
- Protection
- Secretion
- Absorption
- Excretion
- Sensory receptors
- Filtration
- Lubrication
- sheet-like arrangements of extra-cellular matrix proteins
- Interface between support tissues and parenchyma
- structural support
Basement membrane
- attachment of epithelial tissues
- control of epithelial growth and differentiation*
- permeable barrier
- Type IV collagen
- proteins: heparan SO4
Basement membrane
Layers of Basal Lamina
- Lamina lucida
- Lamina densa
- Lamina fibro-reticularis
Components of Basal Lamina
- Type IV ccollagen
- Heparan SO4
- Structural glycoprotein
Structural glycoprotein
- fibronectin
- laminin
- entactin
Membrane Specializations:
- Intercellular
- Lumina
- Basal
Epithelial Tissue Membrane Specializations: Intercellular
- Occluding junctions - tight, zonula occludens*
- Adhering junctions* - zonula adherens, macula adherens
(desmosomes)
** junctional complex - Gap junctions / nexus
Epithelial Tissue Membrane Specializations: Luminal
- cilia – axoneme (microtubules)* , basal body
* doublets (complete (dynein), incomplete - microvilli - microfilaments (ZA), intermediate filaments(MA)
* striated / brush borders - stereocilia
Epithelial Tissue Membrane Specializations: Basal
basement membrane - hemidesmosomes
- selective diffusion, absorption, secretion
- surface specializations (microvilli, cilia)
Simple Epithelium
- Simple epithelium
- Layering of nuclei
- Resting on basement membrane
- In respiratory passages, male uro-genital tracts, female excretory ducts
- Membrane specializations
Pseudostratified epithelium
- loose collagenous
- fibroblast , mast cells , macrophages
Papillary layer
- dense irregular c.t.
- blood and lymph vessels
- skin appendages
Reticular layer
Basal - cuboidal Intermediate - polygonal Surface – rounded / flat 1. large, pale, scalloped 2 . thickened 3. ½ nuclei, large, round, prominent nucleoli
Transitional Epithelium
Specialized to synthesize and secrete a specific product (Proteins, Lipids, CHO+CHON)
Glandular Epithelium
Glandular Epithelium: Number of cells
- Unicellular gland - Goblet cells- mucigen
2. Multicellular gland
Glandular Epithelium: Manner of secretion
- Endocrine – without ducts into blood / lymph
- Exocrine – with ducts
- Paracrine – paraneurons , into the ECS
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
Glandular Epithelium: Nature or Characteristic or Type of secretion
- Serous gland
- Mucous gland
- Mixed gland
- Cytogenic gland
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
4 Fundamental Tissues
- Epithelial
- Connective
- Muscular
- 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
- Extra cellular matrix - Consist of protein fiber and ground substance
- 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:
- Fixed cells = more or less permanent resident population
e. g. Fibroblasts, mesenchymal cells, reticular cells, fat cells - 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
- Fibril-Forming Collagens
- Sheet-Forming Collagens
- 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)
- Glycosaminoglycans (GAG)
- Proteoglycans
- 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
- Connective Tissue Proper
- Embryonic Connective Tissue
- 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
- Storage of fat
- Insulation against heat loss
- Mechanical support in certain body regions
2 Types of Adipose Tissue
- 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
- Hyaline cartilage (Type II collagen)
- Elastic cartilage (Type II collagen, elastic fibers)
- 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)
- Capsular (pericellular) matrix –located immediately around the chondrocyte
- Territorial matrix - it surrounds the isogenous group
- 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
- Collagen Molecules - (Type II collagen)
- Proteoglycans (3.5X106 daltons)
- Glycosaminoglycans (GAGs) - Chondroitin sulfate, Keratin sulfate, hyaluronan
- Aggrecan - Proetin Core - Multiadhesive glycoproteins
(non collagenous and non proteoglycan-llinked glycoproteins, CHONDRONECTIN)
4 Zones of Articular Cartilage
Divided into four (4) zones:
- Superficial (tangential) layer - Elongated and flattened chondrocytes surrounded by a condensation of collagen II
- Intermediate (transitional )zone - Round chondrocytes randomly distributed
- Deep (radial) zone - Small , round chondrocytes, in short columns perpendicularly arranged
- 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
- Appositional Growth: Deposition of new cartilage on the surface of existing cartilage.
- 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
- Glycoproteins
Osteonectin –serves as glue between the collagen and hydroxyappatite crystals - 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
- Osteocalcin- captures calcium from the circulation and attracts and stimulates osteoclasts in bone remodelling
- Protein S – assists the removal of cells undergoing apoptosis
- 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?
- Osteocytes - Osteoprogenitor cells
- Osteoblasts - Bone lining cells
- 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 boneand 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 marrowwhere hematopoiesis occurs
Spongy Bone
What are the different bone cavities?
- Endosteal cells (osteoblastics and bone-lining cells)
- flattened in shape with elongated nuclei and indistinguishable cytoplasmic features
- Difficult to distinguish at the microscopic level - 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
- 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
- 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
6
Endochondral Ossification
- Formation of Bone Collar
- Cavitation of the hyaline cartilage
- Invasion of Internal cavities by the peristyle
- Formation of medullary cavity
Mechanism of bone repair
- Hematoma formation
- Fibrocartilaginous Callus formation
- Bony callus formation
- Bone remodelling