Histology of Muscle, Cartilage and Bone Flashcards
What are 3 main features of skeletal muscles
Straited
Unbranched
Multinucleate
What are the periphery of skeletal muscle fibres
Nuclei (just under cell membrane)
What is another name for the cell membrane that encloses each muscle cell
Sarcolemma
Skeletal muscle fibres are grouped into bundles called what?
fascicles
What is the name of the connective tissue that surrounds the muscle as a whole called?
Epimysium
What is the name of the connective tissue around a single fascicle called
Perimysium
What is the name of the connective tissue around a single muscle fibre called?
Endomysium
Describe the diameter of skeletal muscle fibres
Consistent and very little variation
What aer the unit of contraction of muscle cells
Sarcomeres
Sarcomeres are placed end to end to form what in a typical muscle cell
Myofirbril
What type of filaments are anchored at the z disc?
Actin filaments
Why do skeletal muscles appear striated?
The sarcomeres in the myofibrils with their alternating dark and light bands are held in registry with one another across the fibre. I.e. the Z disks in the sarcomere of one myofibril will be aligned with the Z disks of the sarcomeres in the surrounding myofibrils.
Why do skeletal muscles and cardiac muscles look different even though they are both striated
The accuracy in cardiac muscles is not as good as it is in skeletal muscles
What does a motor unit consist of
1 motor neurone and all of the muscle fibres that it innervates
Describe the control of movement based on the number of muscle fibres in a motor unit
The fewer the number of muscle fibres in a motor unit, the fibre the control of movement
What does the axon of the motor neurone do as it nears its termination
It branches
What does each axon branch end in ?
A special type of synapse called the neuromuscular junction
How often is a muscle fibre touched?
Only once, regardless of its size
How many types of skeletal muscle are there?
What is the difference between these
3
Based on differences in the biochemistry, morphology and physiology of the fibres
Describe Type 1 skeletal muscle
relatively slowly contracting fibres that depend on oxidative metabolism.
Abundant mitochondria and are resisitant to fatigue
Red fibres
Great force but slow contracting
High conc. of myoglobin
Describe type IIa skeletal muscle
Intermediate between type I and TypeIIB
Relatively fast congtracting but are also reasonably resistant to fatigue
Uncommon fibres
Describe type IIb skeletal muscle
Fast contracting fibres that depend on anaerobic metabolism Few mitochondria Fatigue relatively easily Produce great force Called white fibres Low myoglobin
What stain can be used to determine the different types of skeletal muscle
Succinate dehydrogenase stain
List some of the features of cartilage
Semi-rigid and deformable
Permeable
Avascular
Cells nourished by diffusion through the extracellular matrix
List some features of bone
Rigid
Not permeable
Cells within the bone must be nourished by the blood vessels that pervade the tissue
What are cells gound in cartilage called
Chondrocytes (chondroblasts when immature)
Where do chondrocytes live
Within a space in the extracellular matrix termed a lacuna
What do chondrocytes do?
they are active cells which not only secrete but also maintain the extracellular matrix around them
What is the most common form of cartilage
Extracellular Matrix in Cartilage (hyaline)
What is ECM made from
75% water and 25% organic material
What type of collagen is found in most connective tissues?
Type 1
What does Type II collagen form
A 3-meshwork
Describe the colour of Hyaline cartilage
Blue-white in colour and translucent
Descibe the colour of Elastic cartilage
Light yellow in colour
What makes elastic cartilage flexible
The addition of elastic fibres
Describe the colour of fibrocartilage
Appears White
What type of cartialge contains bands of densely packed type 1 collagen interleaved with rows of chondrocytes surrounded by small amounts of cartilaggenous ECM?
Fibrocartilage
Where is hyaline cartilage found?
Articular surfaces Tracheal rings Costal cartilage Epiphyseal growth plates Precursor in fetus to many bones
What are 5 functions of bone
Support Levers for effective movement Protection of internal organs Calcium sotre (more than 95%) Haemopoiesis (blood cell production)
What is the main composition of one
Mineral (calcium hydroxyapatite crystals)
What makes up the shaft (diaphysis) of long bones
An outer shell of dense cortical bone
What occupies the ends of the bone (epiphyses)
Cancellous or trabecular bone
What is the main difference between bone cells and the matrix
The presence of spaces adjacent to trabecular bone (marrow cavities)
What is the name given to living cells in bone
Osteocytes
What is the term given to the lines that are often visible surrounding the osteon
Cement lines
What is the purpose of osteoprogenitor cells and where are they located?
Serve as a pool of reserve osteoblasts located on bone surfaces - e.g. under the periosteum
What are osteoblasts and where are they located
Bone forming cells found on the surface of developing bone
What are osteocytes
A bone cell trapped within the bone matrix
What are osteoclasts
Large, multinucleated cells
They are found on the surface of bone and are responsible for bone resorption
Where are osteoclasts believed to be derived from?
THe macrophage lineage of cells
What 4 things doe osteoblases secrete which are all colectively termed osteoid
Collagen
Glycosaminoglycans (GAGs)
Proteoglycans
Other organic components of the matrix
Why does the bone that is laid down during devlopment of following a break differ from normal lamella bone
Because rather than having collagen fibres orientated all in one direction, the collagen fibres are laid down in a haphazard fashion. This is called woven bone
What is the main difference between woven and lamellar bone
Woven is not as strong as lamellar bone
What happens to woven bone over time
It is broken down by osteoclasts and reformed by new osteoblasts
