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Histology questions Lecture 4


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What are the functional differences in skeletal tissues based on?
The different nature and proportion of:
1) ground substance
2) fibrous elements
... in the ECM.
The design of bone are what two things?
1)Optimally provide maximum strength for the least weight.
2)Change in relation of how much stress is placed on the bone.
What are both bone and cartilage derived from?
Mesenchyme of the embryo.
What are the functions/ uses of Cartilage?
1) Protect soft tissues
2) Proved a sliding surface in joints
3) Help in Development and growth of long bones
4) Repair bone injury.
How is cartilage different from bone in terms of nurishment?
Cartilage has no nerves, blood suply, or lymphatic system.
What is the main factor that gives cartilage it's characteristic?
It's high water content.
If cartilage is avascularized, then how do the cells get nourishment?
Diffusion from the capillaries in the PERIOCONDRIUM or synovial fluid.
What does the low Oxygen content of Cartilage tell us about cartilage
It uses anaerobic glycolysis and has a low metabolism, thus it is slow at repairing an injury.
What two types of cells are there in cartilage?
CHONDROBLASTS - actively synthesize and deposit extracellular matrix components and fibers, however it is not yet trapped with in the matrix.
CHONDROCYTES - Mature cells of cartilage, which are completely surround by matrix.
Where do CHONDROCYTES reside?
What is the capsular sheath that surrounds most cartilage and what is it made of?
Perichondruim, which is made of dense connective tissues.
What are the four principal components of the ECM in cartilage.
1) Collagen (Type II)
2) Hyaluronic acid
3) Proteoglycans
4) glycoproteins
What special ingredients are added to make fibrous and elastic cartilage?
Elastin = E.C.
Collagen (type I) = F.C.
What is the definition of tensile strength?
The ability to distribute weight and resist breakage
What is the composition of the ground substance between the fibers and cell bodies of cartilage and what properties does this give cartilage?
Composition: Highly hydrated forms of Proteoglycans

Properties: Gives the Cartilage firmness and resiliency.
What is a proteoglycan comprised of?
Polypeptide chains glycosidically-linked with glucosaminoglycans.
Glucosaminoglycans are primarily condroitin sulfates and keratan sulfates. Individual proteoglycans attach to hyaluronic acid strands to make an aggregate.
What are the three types of cartilage?
1) Hyaline
2) Elastic
3) Fibrocartilage
What are some facts about Hyaline Cartilage?
1) It is the most widespread cartilage in the body
2) Most of bones were formed by replacing the hyaline model by endocondral bone formation.
3) In adults H.C. is found in the larynx, trachea, bronchi, ribs, and on articular surfaces of bone.
How does Elastic cartilage differ from Hyaline and where can it be found?
E.C. differs from H.C. because of its high concentration of elastin. This gives it flexibility and resiliency.
It can be found in the external ear, Eustachian tube, and the epiglottis.
How does Fibrocartilage differ from the other types of cartilage and wher can it be found?
Fibrocartilage differs due to the prominent bundles of collagen fibers(type I). This gives it great tensile strength.
It is found ins areas subject to high frictional forces, such as the intervertebral discs, pubic symphysis, and temporomandibular joint.
How is bone distinguished from cartilage?
1) Bone has the inorgainc calcium salts in its ground substance, which makes the matrix rigid. This makes the bone a reserve of Calcium.
2) Bone is vascularized, and contains nerves and a lymphatic system.
3) Bone is not as flexible as cartilage, however, the tensile strength is much greater.
What are the three types of cells found in bone?
Osteoblasts, Osteocytes, Osteoclasts
Where are osteoblasts found and what do they produce?
The can be found both internally and externally, since they arise from both the periosteum and endosteum. The Osteoblasts produce type I collagen.
What are osteocytes and where can they be found?
Osteocytes are osteoblasts trapped in by matrix. Osteocytes can be found within small canals called CANALICULI.
What are osteoclasts and what are their function?
osteoclasts are multinucleated cells which come from the fusion of bone marrow-derived precursors. They remodel the bone through reabsortion of both the mineral and organic components of bone.
What is the outer surface of bone made up of?
Fibroblast-like cells called the periosteum.
What is the meaning of osteoprogenitor cell?
A cell that can differentiate into osteoblasts.
What are the inner surfaces of bone lined with and how thick is it normally?
Endosteum and it is about one cell thick.
What is the ratio of inorganic salts and organic matrix in bone?
~65-70% Inorganic salts
~30-35% Organic Matrix.
What is the makeup of the organic matrix of bone?
1) ~90% type I collagen
2) Proteoglycans
3) Specific and non-specific bone proteins (other than collagen).
What are examples of specific bone proteins found in the organic matrix?
1) bone sialoproteins
2) ostenecin
3) osteocalcin.
What is the primary make up of the inorganic component of bone?
What is primary bone and what are its other names?
It is the first bone formed in the fetus and also the bone formed in repairing an broken bone. It is also known as woven bone or immature bone.
What characteristics are there primary bone and where can it be found in an adult?
1)Primary bone is temporary and arranged in irregular arrays of collagen fibers. It contains a lower ratio of inorganic to organic tissues than normal bone.
2) It can be found in tooth sockets and some tendon insertions.
What are some differences in the structure of compact/dense bone and spongy/cancellous bone?
Compact Bone has a defined concentric pattern of different layers called lamellae which cellter round a blood supply.
What type of canals are there in compact bone?
1) Volkmann's canals which run horizontally to the bone structure and
2) Haversian canals which run vertically.
Both canals interconnect with each other to for a maze like structure.
What run through the Haversian and Volkmann canals?
Blood supply, nerves and lymphatics.
Where is the circumferential lamellae and what makes it?
It is on the outer layer of the compact bone and it is made by osteoblasts from the periosteum.
What are Haversian Systems? (AKA Osteons)
They are the function unit of bone made up of ~5-20 concentric circles of lamellae. They are continually remodeled and the lamellae that are left behind make up the interstitial lamellae
What are the two ways that bone can grow?
1) Intramembranous Ossifcation
2) Endochondral Ossification
What are the facts of Intramembranous Ossification?
1) Mostly in the bones of the skull and face
2) Osteoblasts lay down bone until they are surrounded by the matrix
3) If it occurs at the out ends of the bone it is called appositional growth and this is the process responsible for makeing long bones grow.
What are the six steps in Endrochondral Ossification?
1) A Hyaline model is formed
2) The shaft is surrounded by intramembraneous bone and starts to calcify the cartilage
3)The diaphysis is innervated by blood vessals and mesenchymal cells which become osteoprogenitor cells, which become osteoblasts.
4) The cartilage is reabsorbed by osteoclasts, while the calcified matrix is being secreted by osteoblasts
5) A secondary ossification center starts in the epiphyses, creating a epiphyseal plate
6) The epiphyseal plate slowly disappears as growth finishes of the long bones.
A bone can grow both in length as well as in width, which is responsible for what?
Width = intramembranous/apposition
Length = Endochondrial
What are the five layers of the epiphyseal plate?
1) Resting Zone - Cartilage cells, no Mitosis
2) Proliferative Zone - Cartilage cells are proliferating
3) Hypertrophic Cartilage zone - cells are hypertrophing
4) Calcified cartilage zone - matrix is becoming calcified
5) Ossification zone - the Ca matrix is remodeled and bone is layed down.

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