Histology Flashcards
Describe the location of the nuclei in muscle fibres and explain why they are found there
Found at the periphery of the cell as the cell is so packed with actin and myosin that the nuclei are pushed to the side
What is a syncytium?
A mass containing several nuclei
Myofibrils are grouped into bundles called…
Muscle fibres (the skeletal muscle cell)
Muscle fibres are grouped into bundles called…
Fascicles
Fascicles are grouped into…
The final skeletal muscle
Myofibrils -> muscle fibres -> fascicles -> skeletal muscle
What is the connective tissue that surrounds... - the muscle as a whole - a single fascicle - a single muscle fibre ...called?
Epimysium (whole muscle)
Perimysium (single fascicle)
Endomysium (single muscle fibre)
What causes the perpendicular striations seen in skeletal muscle fibres?
The z-lines of the sarcomeres inside the myofibrils are aligned from one myofibril to the next
Describe each of the following regions of the sarcomere:
- I band
- A band
- H band
- M line
- I band = zone of just actin
- A band = the entire length of myosin (so includes some actin)
- H band = zone of just myosin
- M line = line down the centre of the sarcomere
What are the 3 types of skeletal muscle fibre?
Type I
Type IIa
Type IIb
Describe type I fibres (aka ‘red’ fibres) in terms of speed of contraction, metabolism and resistance to fatigue
- Slow contracting fibres with weak force
- Oxidative metabolism (so require lots of mitochondria and myoglobin)
- Good resistance to fatigue
Describe type IIa fibres in terms of speed of contraction, metabolism and resistance to fatigue
- Relatively fast contraction
- Reasonably resistant to fatigue
(these fibres are uncommon)
Describe type IIb fibres (aka ‘white’ fibres) in terms of speed of contraction, metabolism and resistance to fatigue
- Fast contracting fibres with great force
- Anaerobic metabolism (so have fewer mitochondria and myoglobin)
- Fatigue easily
Describe the difference in the way that cartilage and bone receive their O2 and nutrients from blood
Cartilage is permeable so O2 and nutrients can diffuse through the ECM, therefore it is avascular
Bone is impermeable so blood vessels must be embedded in the tissue to supply it with O2 and nutrients
What are chondrocytes and where are they found?
- Chondrocytes secrete and maintain the ECM of cartilage
- Each chondrocyte lives inside its own little space in the ECM called a lacuna
ECM in hyaline cartilage is composed of 75% X, 15% Y and 5% Z
75% water
15% type II collagen (a finer type of collagen that helps resist tearing)
5% proteoglycan
Name and briefly describe the 3 different types of cartilage
Hyaline cartilage -> most common type, found in joints and trachea, blue-white and translucent
Elastic cartilage -> lots of collagen has been replaced with elastic fibres so more flexible, found in ear tip, light yellow colour
Fibrocartilage -> hybrid between hyaline cartilage and tendon, very strong, white in colour
Give examples of where hyaline cartilage is found
- Articular surfaces (joints)
- Tracheal rings
- Costal cartilage
- Epiphyseal growth plates
- Precursor to many bones in fetus
Describe calcium storage in bone
- > 95% of total calcium in the body is found in bone
- There is a constant exchange of calcium between bone and the blood
Describe the different locations of haemopoiesis in the body throughout a human lifetime
In utero -> liver and spleen
At birth -> all bone marrow
By early 20’s -> only bone marrow of axial skeleton and limb girdle
Bone is composed of 65% W, 23% X, 10% Y and 2%Z
65% bioapatite (mostly hydroxyapatite)
23% collagen (mainly type I)
10% water
2% non-collagen proteins
Name and describe the 2 types of bone that can be seen in a longitudinal section of long bone
Cortical/compact bone -> makes up the dense, ivory-like outer shell
Cancellous/trabecular bone -> spongey, mesh-like bone that occupies the ends of the bone
What are the proper names for the... - shaft - neck - head ... of a long bone?
Shaft = diaphysis
Neck = metaphysis
Head = epiphysis
What is lamellar bone?
The main type of bone in the human body
It is characterised by its orderly arrangement of collagen bundles to form alternating circular layers
Describe the following features of lamellar bone:
- Outer circumferential lamellae
- Inner circumferential lamellae
- Osteon
- Outer circumferential lamellae = circuits the entirety of the outer circumference of the bone
- Inner circumferential lamellae = circuits the entirety of the inner circumference of the bone
- Osteon: a circuit of lamellae within the cortical bone which has a central Haversian canal