Skeletal connective tissue L5 Flashcards
What is specialised connective tissue characterised by
Dominance of matrix
What are the 3 types of specialised connective tissue?
Cartilage: semisolid matrix (semi-rigid structure), bone: calcified matrix and blood: liquid matrix
What does cartilage consist of?
Cells (chondrocytes) which occurs within spaces in the matrix called lacunae, fibers which is a dense network of collagen and/or elastin fibers and matrix (proteoglycans, ground substance)
What is function of lymphatic system?
to remain normal blood volume and other liquids
What are the 3 cartilage cells?
Mesenchymal cell and chondroblasts and chondrocytes
What is the function of mesenchymal cells?
Differentiate into chondroblasts
What are the 5 steps of cartilage formation:
- Chondrification - genesis. Mesenchymal cells differentiate chondroblast
- Chondroblasts proliferate and synthesise ground substance and fibrous extracellular matrix
- Chondroblasts separate into spaces (lacunae)
- More divisions form clusters (isogenous gaps)
- These chondrocytes are embedded in extracellular matrix
What must you remember in regards to B and C
B BEFORE C = chondroBlasts before chondroCytes
What is ossification?
When cartilage is replaced by bone in the body
What are the 2 methods of growth in cartilage?
Appositional growth and interstitial tissue growth
What is interstitial tissue growth?
Increasing in LENGTH; specific for endochondral bone formation; chondrocytes divide and secrete matrix from
within their lacunae
How many bones in an adult?
206 bones
How many bones in infants?
About 300
What are the 8 bone functions?
- Support
- Movement
- Protection
- Hematopoiesis
- Mineral storage
- Acid-base balance
- Detoxification
- Sound transduction
What is hematopoiesis?
Makes red blood cells in red bone marrow
What is the mineral storage in bone?
Acts as a calcium reservoir, maintaining calcium and phosphorus equilibrium
What does the acid-base balance do in bone?
Buffers blood against excessive pH changed by absorbing or releasing alkaline salts
What does the function of detoxification do in bone?
Stores heavy metals and foreign elements.
What is sound transduction?
In mechanical aspect of hearing
What are the 2 types of bone? HINT C+C
Cortical/compact bone and Cancellous/Trabecular/Spongy bone
What % of skeletal mass is cortical bone?
80%
What is the physical description of cortical bone?
Dense protective shell
What is the location of cortical bone?
Around all bones, beneath periosteum. Primarily in the shafts of long bones
What % of skeletal mass is cancellous bone?
20%
What is the function of the periosteum?
Periosteum’s function is to nourishes the bone, it is rich in nutrients and capillaries.
What is the location of the cancellous bone?
In the vertebra, flat bones for example the pelvis and the ends of long bones
What is the physical description of cancellous bone?
Rigid lattice designed for strength; Interstices are
filled with marrow
What can osteoprogenitor cells do?
Osteoprogenitor cells means it can divide and make new cells
What are the 4 types of bone cells?
Osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts
What is the function of osteoprogenitor cells?
Form bone stem cells and make osteoblasts and osteocytes
What is the function of osteoblasts?
They are bone forming cells and immature bone cells that have lots of rough ER for collagen synthesis
What is the function of osteocytes?
Act as inactive osteoblasts and they are the most abundant cell found in bone
What is the function of osteoclasts?
They are phagocytic cells that erode bone and bone resorption and remodelling
What happens at bone fractures?
When a bone fractures a blood clot forms at fracture site (6-8h) and this is replaced by collagen tissue. Then chondroblasts lay down cartilage (provisional callus) (2-3 weeks). Osteoblasts then lay down woven bone
(bony callus) (3-4 months). This bony callus then remodelled to mature lamellar bone
What are the 5 types of fractures?
Simple, stress, comminuted, greenstick, compound/impacted
What are the 2 types of ossification/osteogenesis?
Intramembranous ossification and endochondral ossification
Where is 99% of the body’s Ca^2+ ?
In bone approx 1kg
What is ossification/osteogenesis?
Modelling bone
What are the 2 Ca^2+ compartments?
Bone fluid and Mineralised bone
What happens in the bone fluid Calcium compartment?
Fast exchange of calcium by pumps
What happens in the mineralised bone compartment of Calcium?
There is a slow exchange by bone resorption and osteoclasts phagocytic activity is increased and the Calcium ions are released during low Ca^2+ levels
Greenstisck happens a lot in children, where 1 side of bone is broken and other part is not
What does a stress fracture mean?
stress fracture is when it keeps breaking
What are the 8 hormones that regulate bone growth and loss?
Vitamin D, Growth hormone, Oestrogen, Calcitonin, Cortisol, Parathyroid hormone (PTH), thyroid and Vitamin A
Which hormones are associated with bone growth?
Vitamin D, Growth hormone, Oestrogen and Calcitonin
How do hormones regulate bone growth?
They activate osteoblasts and inhibit osteoclast function
How does vitamin D regulate bone growth?
By promoting osteoblast differentiation
How does Growth hormones regulate bone growth?
By promoting osteoblast functions
How does Oestrogen regulate bone growth?
Inhibits osteoclast
How does Calcitonin regulate bone growth?
Inhibits osteoclast
What is cartilage?
It is a semi-rigid dense connective tissue that is surrounded by a membrane called the perichondrium
Does cartilage have lymphatic vessels?
No
Is there blood vessels or nerves in cartilage?
No blood vessels (avascular) or nerves except in perichondrium
What is cartilage nourished by?
Diffusion or gases and nutrients
What is the function of chondroblasts?
To make ground substance and matrix
What is the function of chondroblasts?
To make ground substance and matrix
What is the function of chondrocytes?
Mature cells, embedded in matrix
Where is the skeletal system derived from in embryogenesis?
The mesoderm germ layer, most skeleton is cartilage
What is appositional growth?
Increasing in GIRTH or WIDTH; chondroblasts deposit
collagen/matrix on surface of pre-existing cartilage
What do chondrocytes occupy?
Hallow space
What do chondrocytes make?
Ground substance and fibrous elements
What are chondrocytes surrounded by?
Its own secreted matrix
What are 3 types of cartilage?
Hyaline, elastic and fibrocartilage
What is hyaline cartilage?
It is the most abundant cartilage that provides support through flexibility. Known as “glassy”. Found in articular cartilages and costal cartilage, larynx, trachea and nose.
What is elastic cartilage?
It has many elastic fibers and is able to tolerate repeated bending. Found in ear and epiglottis.
What is fibrocartilage?
Fibrocartilage resists strong compression and strong tension. It is an intermediate between hyaline and elastic cartilage. It is found in intervertebral disks and pubic symphysis.
What type of cartilage shows the most damage? Talk about all 3(4)
Hyaline cartilage is easily damaged and has limited repair whereas elastic and fibrocartilage shows less damage or aging. Articular cartilage does not repair.
Why does cartilage have limited repair capabilities?
Chondrocytes are bound in hallow spaces and they cannot migrate to damaged areas to make new matrix
What is damaged cartilage replaced by?
Fibrocartilage scar tissue
Why is there no issue of rejection with a cartilage transplantation?
The antigenic power of cartilage is low and the immune system cells poorly diffuse cartilage
What is arthritis?
Arthritis is the degeneration of cartilage joints (articular cartilafe)
What is dwarfism?
Dwarfism is the reduced proliferation of chondrocytes
What is a herniated disk?
Herniated disk is when a disk cartilage ring ruptures, pushing into the spine.
What are tumours (within skeletal connective tissue?
Cartilage cells give rise to benign known as chondroma tumours. Malignant tumours do not usually occur in cartilage they happen in bone.
What is scurvy?
Lack of Vitamin C needed to make collagen which results in defective cartilage and bone
What is polychondritis?
The inflammation and degeneration of cartilage
What is chondromalacia?
The degeneration of joint cartilage (at knees)
What is chondrodysplasia?
Hereditary bone dysplasia
What is Costochondritis?
Inflammation of rib cartilage causing chest pain
What is Tietze’s syndrome?
Inflammation of cartilage that joins ribs to breast bone
What is bone matrix composed of and in what percentages?
Organic materials (20%), Inorganic materials salts (70%) and water (10%)
What inorganic materials salts is bone matrix made up of?
Mainly calcium and phosphate in the form of hydroxyapatite crystals
What organic materials is the bone matrix made up of?
i.e. Osteoid from osteoblasts. Type 1 Collagen fibers (90% of organic osteoid part), Glycosaaminoglycans and Ground substance proteoglycans
What are the types of fixed macrophages? HINT THERE ARE 6
- Dust/Alveolar type (lungs)
- Histiocytes (connective tissue)
- Kupffer cells (liver)
- Microglial cells (nervous)
- Osteoclasts (bone)
- Sinusoidal lining cells (spleen)
What do Osteoclasts (phagocytic cells) secrete?
They secrete organic acids and lysosomal proteolytic enzymes to erode bone
What are the 4 steps of bone formation?
- Osteoblasts make and secrete collagen and organic matrix (osteoid)
- Osteoid then becomes calcified i.e. calcium deposition
- Osteoblasts secrete vesicles of alkaline phosphatase (AP)
- AP cause matrix mineralisation (gives rigidity and strength)
What are bones?
Bones are solid network of living cells
What happens in rickets and chronic renal failure in regards to calcium and phosphate levels?
There is inadequate calcium and phosphate ions in osteoid tissue and minerlaisation is low
What is a mature type of bone and what are the 2 parts?
Mature describes an adult bone and can be compact or spongy. Also called lamellar bone
What is a compact mature bone?
It is arranged in Haversian systems; found as dense layer on outside of bones
What is a spongy mature bone?
It is trabecular in appearance and it is found in interior of the bone
What is an immature a.ka. woven bone?
It is bone tissue initially deposited in skeleton in fetal life or after a fracture. Nonlamellar (woven), is irregularly arranged collagenous fibers in proteoglycan matrix
Why does immature bone stain more intensely with hematoxylin?
Since it is not mineralized
What is a long bone and what does it consist of?
Long bones are like the tibia and metacarpals. Consists of diaphysis, epiphysis, metaphysis and epiphyseal plate.
How is long bone grown?
Growth by endrochondral ossification
What is the diaphysis part of long bone?
It is the shaft consisting of marrow cavity surrounded by compact bone (little spongy bone between compact bone and marrow)
What is the epiphysis part of long bone?
It is the expanded end; mainly spongy bone surrounded by thin outer shell of compact bone
What is the metaphysis part of long bone?
It is the flared portion between diaphysis and and epiphysis
What is the epiphyseal plate part of long bone?
It is the cartilage that separates epiphyseal and diaphyseal cavities which maintains growth process
What is flat bone?
Thin and plate like, bones of skull and sternum; growth by intramembranous ossification
What does intramembranous ossification involve?
The direct chondrocytes lay down bone.
How are intramembranous ossification fractures dealt with?
Fractures are treated with internal fixation with screws/pins
What does endochondral ossification involve?
It involves cartilage as a precursor.
How are endochondral ossification fractures treated?
Fractures of long bones are treated by plaster of Paris
Which is the most common in terms of fracture healing?
Endochondral ossification
What are the 5 types of fracture?
- Simple
- Compound / impacted
- Comminuted
- Greenstick
- Stress
