Anatomy: Histology Flashcards
What are the canaliculi of bone?
Interconnect the lacunae (where the osteocytes are located)
Describe the structure of a skeletal muscle fibre
Long cylinders which are striated, unbranched and multinucleated
Name the functional unit of bone
Osteon
During bone remodelling, what is the basic multicellular unit?
The collection of osteoclasts and osteoblasts that participate in bone remodelling at a particular site
What is a Haversian canal?
Found in cortical bone, the Haversian canal transmits small neurovascular and lymphatic vessels to the rest of the osteon
Name the components of bone
65% bioapatite 23% collagen 10% water 2% non-collagen proteins
What is the most common type of cartilage?
Hyaline cartilage
What is a myofibril composed of?
Many sarcomeres placed end to end
What is endochondral ossification?
The process of bone development from hyaline cartilage, involved in all the bones in the body apart from the skull, mandible, and the clavicles
Where do cartilaginous bones ossify first?
Within the diaphysis
Define perimysium
Connective tissue surrounding a single fascicle
What is osteoid?
Collagen, glycosaminoglycans, proteoglycans and other organic compounds of the matrix which is secreted by osteoblasts
Will become mineralised over time to become mature bone
Osteocytes sense what action on the skeleton?
Mechanical strain
What is the mineral of bone?
Principally calcium phosphate crystals, particularly hydroxyapatite
What is lamellar bone?
The bone of the adult skeleton
Consists of highly organised sheets of mineralised osteoid
What is the epiphysis of a bone?
Ends of bone
From what lineage of cells are osteoclasts believed to be derived from?
Macrophages (haematopoietic progenitors)
Where are osteoblasts derived from?
Mesenchymal cells in the bone marrow stroma
Which type of muscle fibre produces a relatively smaller amount of force but is more resistant to fatigue?
Type I
Name the cells found in cartilage
Chondrocytes
What is the epiphyseal plate of bone?
Growth plate
Describe the structure of the extracellular matrix of hyaline cartilage
75% water 25% organic material (60% type II collagen, 40% proteoglycan aggregates)
What is the medullary cavity in bone?
Central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored
What type of cartilage is found in the IV discs?
Fibrocartilage
Describe the structure of fibrocartilage
Hybrid between tendon and hyaline cartilage, bands of densely packed type I collagen interleaved with rows of chondrocytes surrounded by small amounts of cartilaginous ECM, appears white
What are type IIB muscle fibres (‘white’ fibres)?
Fast contracting fibres that depend on anaerobic metabolism - few mitochondria and less myoglobin
How is bone girth increased?
Cells from the periostrum lay down circumferential new bone on the periphery of the existing cortex
What are type I muscle fibres (‘red’ fibres)?
Relatively slowly conducting fibres that depend on oxidative metabolism - lots of mitochondria and myoglobin
How is the structure of trabecular and compact bone similar?
Both types of bone are lamellar (made up of layers)
Define fasicle
Group of muscle fibres; a muscle typically contains several fascicles
Where are the osteocytes located in bone?
Between the lamellae, within lacunae
Which type of bone is found at the epiphysis?
Cancellous or trabecular bone
Name the primary site of haemopoiesis in utero
The liver and the spleen
Describe the structure of elastic cartilage
Light yellow in colour, the addition of elastic fibres (replace lots of ECM) make it quite flexible
What is intramembranous ossification?
The process of bone development from fibrous membranes, involved in the formation of the flat bones of the skull, mandible, and the clavicles
Name the primary site of haemopoiesis after birth and throughout life
Bone marrow
Define epimysium
Connective tissue that surrounds the whole muscle
What are type IIA muscle fibres?
Intermediate muscle fibre between type I and type IIB, relatively uncommon
Name the space in the extracellular matrix where the chondrocytes are located
Lacuna
What are osteocytes derived from?
Osteoblasts which become buried in bone matrix
What are osteoblasts?
Bone forming cells found on the surface of developing bone
What are osteoprogenitor cells?
Pool of reserve osteoblasts located on bone surfaces
What is the main difference between cortical and trabecular bone?
The presence of spaces (marrow cavities) adjacent to trabecular bone
What type of cartilage would be found on articular surfaces, and makes up the tracheal rings and costal cartilage?
Hyaline cartilage
By the age of 20, only the bone marrow of which regions are involved in blood production?
Axial and limb girdle skeleton
What is the periosteum?
Membrane that covers the outer surface of all bones, except at the articular surfaces
What type of cartilage is found in the auricle of the ear, and most of the epiglottis?
Elastic cartilage
Describe the structure of the periosteum
Outer fibrous layer, inner ‘osteogenic’ layer which contains progenitor cells that develop into osteoblasts
What are osteoclasts?
Large (up to 40µm or more) multinucleated cells, found on the surface of bone and are responsible for bone reabsorption
How is bone length increased?
Cartilage proliferation at growth plates between the metaphysis and epiphysis; the cartilage then ossifies
What is the metaphysis of bone?
Region between the diaphysis and epiphysis
Define a motor unit
Consists of one motor neuron and all of the muscle fibres it innervates
Describe the appearance of hyaline cartilage
Blue-white in colour, translucent
Describe cartilage
Semi-rigid and deformable, permeable, avascular, cells nourished by diffusion through the extracellular matrix
Why does bone rely on blood vessels that pervade the tissue for nourishment?
Bone is not permeable
Which type of muscle fibre will produce relatively great force but fatigue easily?
Type IIB
Where are the nuclei located in a skeletal muscle fibre?
At the periphery of the fibre, just under the sarcolemma
What is the significance of the Z line?
Marks the boundary between sarcomeres - the sarcomere extends from one Z line to the next
What are osteocytes?
Bone cells trapped within the bone matrix
Define endomysium
Connective tissue surrounding a single muscle fibre
Name the unit of contraction of the muscle cell
Sarcomere
Name the most common type of bone cell
Osteocytes
If a muscle is required for fine control, will it have a greater or lesser number of muscle fibres in the motor unit?
Lesser number - each motor neuron will innervate a small number of muscle fibers, enabling many nuances of movement of the entire muscle
How does the structure of the sarcomeres result in the striations of skeletal muscle?
The alternating dark and light bands of the sarcomeres are held in registry with one another
What is the diaphysis of a bone?
Long shaft
Which type of bone is found in the diaphysis?
Cortical bone
Why does trabecular bone generally lack Haversian canals?
Because the struts are thin, the osteocytes can survive from contact with the marrow spaces
What is woven bone?
Bone that appears in embryonic development and fracture repair, as it can be laid down rapidly
It consists of osteoid with the collagen fibres arranged randomly
Temporary structure, soon replaced by mature lamellar bone
