Histo Flashcards
What are the 3 types of connective tissue?
1) Loose
Dense:
2) Dense regular
3) Dense irregular
What are 2 examples of regular dense connective tissues?
1) Tendon
2) Ligaments
- parallel and dense arrangement of Type 1 collagen fibres provide tensile strength and strong resistance to forces
What are 4 functions of cartilage?
1) Smooth articular surfaces at bony ends
2) Shock absorber
3) Structural support (eg. ear, trachea)
4) New bone formation
What are chondrocytes?
Cells with secrete collagen II fibres and ground substance.
- basophillic cytoplasm, RER, golgi vesicles
Describe the formation of chondrocytes.
Stellate shaped primitive mesenchymal cells
→ differentiate → rounded chondroblasts
→ divide → chondrocytes
What are 3 components of ground substance?
1) Proteoglycans (aggrecans)
- provides resilience
2) Sulphated glycosaminoglycans (chondroitin sulfate, keratin sulphate)
- provides firmness
3) Hyaluronic acid
Which substance in the matrix accounts for its weight bearing capacity?
Hyaluronic acid
Hyaline cartilage is composed of type __ collagen fibrils. It contains (cells (1)) and (subtances (3)). The matrix is mainly made of _____________ which provides resilience.
Hyaline cartilage:
- Type 2 collagen
- chondrocytes in lacunae in cartilage matrix
- sulfated proteoglycans, non-collagenous proteins, glycoproteins
- 60-80% water → resilience
True or false: Hyaline cartilage is highly vascularised to ensure the efficient clearance of waste products and avoid joint injury.
False.
Cartilage is avascular
- receives nourishment by diffusion through water in ground substance
What are 3 examples of hyaline cartilage and their respective functions?
1) Articular ends of bone
- provides low friction surface
- distributes applied force to underlying bone
2) Costal cartilage
- lubrication for synovial joints
3) Epiphyseal growth plate
- new bone formation
Where do cartilage/chondrocytes arise from? (where are the mesenchymal cell located?)
Perichondrium
What is the perichondrium?
Firmly attached connective tissue surrounding hyaline cartilage
i) inner cellular (chondrogenic) → source of new cartilage cells
ii) outer fibrous layer → dense irregular fibrous connective tissue
Which layer of the perichondrium is lacking in adult cartilage?
Inner cellular/chondrogenic layer
- only outer fibrous left
What are 3 exceptions where perichondrium are not seen surrounding hyaline cartilage?
1) Articular ends of joints
2) Sites of bone formation (epiphyseal plate)
3) Nasal and costal cartilages
What is the main implication of not articular cartilage not having a perichondrium?
Cannot repair when there is damage
What are the 2 forms of cartilage growth?
1) Appositional
- ↑ in diameter
- new cartilage develops at surface of existing cartilage
2) Interstitial
- ↑ in length
- within existing cartilage by division of chondrocytes
When does hyaline cartilage calcify?
At articular cartilage
1) During endochondral ossification
2) Aging
What are 3 reasons for why repair of cartilage is generally poor?
1) Avascularity of cartilage
2) Immobility of chondrocytes
3) Limited proliferation of mature chondrocytes
True or false. Elastic cartilage can be seen on a typical HnE stain?
False.
Special stains (Resorcin fuschin and orcein stains) needed to show elastic fibres
What are 4 examples of elastic cartilage?
1) External ear/pinna
2) External auditory canal
3) Eustachian tube
4) Epiglottis of larynx, apex of arytenoid/corniculate/cuneiform cartilage
What are 2 functions of fibrocartilage?
1) Absorb shock
2) Resist compression and shearing forces
Fibrocartilage:
- (thick/thin) collagen fibres w white fibrocartilage
- abundant type __ collagen, some type ___
- (has/lacks) perichondrium
Fibrocartilage:
- thick collagen fibres w white fibrocartilage
- abundant type II collagen, some type I
- lacks perichondrium
What are 4 examples of fibrocartilage?
1) Intervertebral disc
2) Pubis symphysis
3) Manubriosternal joint
4) Menisci of knee joint
5) Glenoid labrum
6) Acetabular labrum
7) Temporomandibular joint
8) Sternoclavicular joint
What are 3 structural components of a long bone?
1) Epiphysis (end)
2) Diaphysis (shaft)
3) Metaphysis/growth plate in children
What are 2 layers of periosteum?
1) Fibrous outer
2) Osteogenic inner
The marrow cavity holds ______ bones narrow with has ____________ lining.
Marrow cavity:
red/yellow marrow
endosteum lining
What are the 2 types of bone?
1) Compact bone
- outer layer of bones/shaft
- almost no space between layers of bone tissue
2) Spongy/cancellous bone
- interior of bones
- marrow cavities between trabeculae
What are the 2 forms of marrow cavity?
1) Red
- hematopoietic
- in flat, irregular bones and ends of adult femur, humerus
2) Yellow
- fat
- may re-differentiate into red marrow under stress
What are the organic and inorganic components of bone?
Organic: 1/3
- cells
- Type 1 collagen
- Ground substance
Inorganic: 2/3
- Calcium phosphate
- Hydroxyapatite crystals
What are 3 bone cells?
1) Osteoblasts
- form bone matrix
2) Osteocytes
- mechanosensors (detect (i) mechanical load (ii) stress (iii) fatigue-induced microdamage) → trigger remedial response from osteoblasts and osteoclasts
3) Osteoclasts
- large mobile multi-nucleated cells
- needed for matrix resorption during bone growth and remodeling (contains lysosomes)
- ruffled border releases acid phosphatases
What cells do osteocytes arise from?
Osteoprogenitor → Osteoblast → Osteocyte
Where are osteoprogenitor cells found?
1) Inner cellular layer of periosteum and endosteum
2) Walls of haverisian and volkman’s canals
What is the histological appearance of osteoblasts?
Cuboidal/polygonal cells
- oval nucleus and basophilic cytoplasm
- newly formed bone surface
How are fibrous/immature/woven bones differentiated from lamellar/mature bones?
Fibrous/immature/woven bones:
- seen in embryonic life and fracture healing
Lamellar/mature bones:
- secondary bones
- lamellar pattern of fibre arrangement
What are the components of the Osteon (Haversian) system?
1) Central canal
2) Concentric lamellae
3) Osteocytes
4) Canaliculi
5) Perforating canals
- contain neurovascular bundles & run perpendicular to central canals to connect them
6) Circumferential lamellae
i) External (internal → periosteum)
ii) Internal (internal → endosteum)
7) Interstitial lamellae
What are Sharpey’s fibres?
At sites of attachment (to ligaments/tendons), collagen fibres in periosteum that are arranged obliquely or perpendicular to bony surface continuous with ECM
(collagen is usually parallel to surface in periosteum)
What is the characterisitic of trabecular bone?
Lack of osteons
What are the 2 types of ossification?
1) Intramembranous
- mesenchymal (fibrous membranes) → bone
- flat bones
- begins in-utero wk8
2) Endochondral
- Mesenchyme → cartilage → bone
Describe the process of intramembranous ossification.
1) Mesenchymal cells group into clusters → ossification centers
2) Secreted osteoid traps osteoblasts → osteocytes
3) Trabecular matrix and periosteum form
4) Compact bone develops superficial to the trabecular bone and crowded blood vessels condense into red marrow
Describe the process of endochondral ossification.
1) Fetal hyaline cartilage model develops
2) Cartilage calcifies, periosteal bone collar forms arnd diaphysis
3) 1° ossification center forms in diaphysis
4) 2° ossification center forms in epiphyses
5) Bone replace cartilage, except articular cartilage and epiphyseal plates
6) Epiphyseal plates ossify → epiphyseal lines
Epiphyseal plate zones: (superficial to deep)
Reserved cartilage → ________
Proliferating cells → __________
Hypertrophy → _____________
Calcified cartilage → _________
Resorption/ossification → _______________
Epiphyseal plate zones:
Reserved cartilage → small resting cells
Proliferating cells → larger dividing cells
Hypertrophy → large chondrocytes in columns
Calcified cartilage → calcified matrix, chondrocyte apoptosis
Resorption/ossification → removal of calcified cartilage, deposition of new bone
Of the liver enzymes,
↑Osteoblast activity → ↑_______
↑Osteoclast activity → ↑__________
↑Osteoblast activity → ↑alkaline phosphatase
↑Osteoclast activity → ↑acid phosphatase
What are the 2 forms of bone growth and where do they occur?
1) Interstitial (length-wise)
- in epiphyseal plate
- chondrocytes undergo mitosis
2) Appositional growth (diameter/thickness)
- within periosteum
Describe the process of fracture repair?
1) Hematoma formation
- mass of clotted blood
2) Callus formation
- “Soft callus” (cartilaginous) splint
3) Bony callus formation
- “hard callus” (spongy bone)
4) Bone remodelling
- spongy bone of hard callus replaced with compact bone
What are the hormones that affect bone homeostasis?
1) Thyroid → stimulate osteoblasts → ↑growth
2) Calcitonin → inhibit osteoclast → ↓breakdown
3) PTH → stimulate osteoclast → ↑breakdown
4) Androgens → stimulate osteoblasts → ↑bone formation
5) GH → Somatomedin → growth of cartilage @ epiphyseal plate
What is osteopetrosis?
↓osteoclastic activity
What is osteoporosis?
Bone resorption»_space;» Bone formation
What is osteogenesis imperfecta?
Inadequate osteoblastic activity → inhibit deposition process in osteons
What is Paget’s osteitis deformans?
Remodelling activity greatly accelerated (both osteoblasts and osteoclasts are active)
