Unit 2 - Skeletal System Flashcards
What is the difference between axial and appendicular skeletons?
Axial: skull, vertebral column, ribs
Appendicular: appendages
What is the function of the skeleton?
Support
Protection
Leverage/movement (attachment site for skeletal muscles)
Blood cell production (‘hematopoiesis’)
Mineral storage (particularly calcium)
Bone connective word?
Os/Osteo
Bone characteristics?
- Second hardest substance in body (enamel first)
- Living, changing tissue
- Remodels/repairs itself based on stresses
How are bones made?
Consist of cells in a matrix:
- Start out as osteoblast -> produce a soft matrix made of collagen fibers in ground substance
- Ossification occurs: osteoblasts harden the matrix by adding minerals (calcium and phosphate)
- Osteoblasts become trapped in small spaces in matrix called lacunae
- Osteoblasts are now considered osteocytes (mature cell)
Why is calcium so important in the body?
Required for muscle contraction, blood clotting, milk secretion, and skeleton
Blood calcium is carefully maintained (to allow these functions) by:
- 2 hormones: calcitonin in thyroid (stops calcium from getting too high by placing in bones), and parathyroid (stops calcium from getting too low by removing it from bones)
What are the 3 major types of cells in bone?
Osteoblast: cells that form bone (secrete matrix and add minerals to ‘ossify’ it)
Osteocyte: osteoblasts trapped in the ossified matrix
Osteoclasts: cells that eat away at bone, important for remodeling (make it healthy so new bone can be created)
What are the 2 types of bone?
Compact bone
Cancellous (spongy) bone
What are examples of a long bone?
Humerus
Femur
Tibia
Fibia
Ulna
What are characteristics of compact bone?
Dense, strong
Makes up shaft of long bones and outer layer of all bones
Permeated by microscopic tunnels, channels, and interconnecting networks surrounded by a hard matrix (bone is nourished and maintained through these tunnels)
What is the Osteon/Haversian System?
The functional and structural unit of compact bone
Contains 1-2 capillaries
Around each central haversian canal are concentric rings of matrix (‘lamellae’)
Small hollow cavities called lacunae that contain osteocytes
What are canaliculi?
Part of Haversian System
- Continuous network of communicating cells that join the central canal to the lacunae and adjacent lacunae to each other (nourishment and exchanged, direct the osteocytes through).
- Groups of osteons lie in a parallel arrangement
- Perforating (Volkmanns) canals penetrate the bone and connect the central canals to adjacent osteons
What are characteristics of cancellous bone?
Lies adjacent to compact bone and is continuous with it (no clear line, blends together)
Primary feature is trabeculae or spicules = series of branching overlapping plates of matrix
What are trabeculae/spicules?
Series of branching, overlapping plates of matrix
- Interconnecting cavelike spaces between plates that store fat and hematopoietic tissue of bone marrow
Reduce the weight of bones so we can move
Arranged to provide support against forces pulling on the bone
Lacunae and blood vessels distributed throughout, provide nourishment to osteocytes
What are long bones?
Greater in one dimension than the other (long)
Function as levers, support and sites for muscle attachment
Most bones in the leg
What are all the bone shapes?
Long
Short
Flat
Irregular
What are the parts of a long bone?
Diaphysis: shaft, mostly compact bone
Epiphysis: enlarged ends, mostly cancellous bone
Epiphyseal plate: area between diaphysis and epiphysis
Periosteum: tough fibrous membrane that covers the outer surface
Endosteum: similar to periosteum, but lines the inner surface of bone
Articular cartilage: smooth layer of hyaline cartilage covering the articular surface of epiphysis
What is the function of the Epiphyseal plate?
Area between diaphysis and epiphysis, cartilage in young growing bones (weak area when young), allows bone to increase in length
- Ossifies (turns to bone) when animal reaches full size
What is the function of the Periosteum?
tough fibrous membrane that covers the outer surface, except at articular surfaces (where bones are in contact with other bones, covered by cartilage)
- Tightly adhered to outer layer of compact boned, anchored by bundles of collagen fibers embedded in outer lamellae
- Outer layer = fibrous connective tissue, inner layer = osteogenic (new bone-forming cells, provide blood vessel access)
- Important for healing and growth in diameter
What is the function of the Endosteum?
Similar to periosteum, but lines the inner surface of bone …….
What is the function of articular cartilage?
Smooth layer of hyaline cartilage covering the articular surface of epiphysis
- Reduces friction and wear in joints
What are the characteristic of short bones?
Cuboid shaped
No marrow cavity, just spongy bone
Absorb shock
eg. tarsus, carpus
What are characteristic of flat bones?
Thin and flat
Function: to protect vital organs
Act as attachments for large muscle groups
eg. ribs, pelvis, skull
What are characteristic of irregular bones?
Misc, any bones that don’t fit into other categories
Sesamoid bones: shaped like sesame seeds
- Embedded in tendons to reduce friction and/or change the course of a tendon
- eg. patella
What are common bone features?
Features that help the bone function, help form joints, provide attachments for muscles/ligaments/tendons
What are the common features on articular surfaces?
Condyles: large round bulge (mainly femur, humerus, and occipital), located at proximal ends
Head: single spherical portion (the ball of ball and socket joints), united with the shaft by a ‘neck’
Facet: 2 flat (slightly concave and slightly convex) surfaces in contact with each other, allow for rocking/twisting (in carpal/tarsal, vertebrae, radius/ulna)
Processes: general term for bumps
- Processes that articulate (head, condyles, facets) have a smooth surface
- Processes without articulating function have rough irregular surfaces (site of muscle/tendon attachments)
- The larger the process, the more powerful the muscular pull on that bone
Holes and depressed areas: foramen (hole for nerves/blood vessels to pass, exception is the pelvis foramen which exists only to decrease weight), fossa (depression in bone for muscles/tendons to occupy)
What are the different processes names?
Trochanter (at femur)
Tubercle (at humerus)
Spine (at spacula)
Just ‘Process’ (eg. spinous process)
Where does blood supply to bone come from?
- Through vessels in the periosteum
- Travel through Volkmann’s canals (right angle to long bone) into Haversian canals (parallel to long axis)
- Allow nutrition to osteocytes
- Nutrient foramen: large channel blood vessels and nerves penetrate
What is a nutrient foramen?
Large channel in bone that blood vessels and nerves penetrate
Where is bone marrow?
Fills the space in the diaphysis of long bone and between spicules in cancellous bones
What are the 2 types of bone marrow?
Red
Yellow
What is red bone marrow?
Hematopoietic tissue
Majority of marrow in young animals
Small part of older animals (ends of long bones, pelvic, sternum)
What is yellow bone marrow?
Mostly adipose tissue
Most common marrow in adults
Doesn’t produce blood cells, but can revert back to red if the body needs more blood cells
What are the 2 ways bone forms?
- Endochondral: grows into and replaces a cartilage network
- Intramembranous: develops from fibrous tissue membranes
What is endochondral bone formation?
Most bones
Start as cartilage -> ossify in center of long bone (primary growth center) -> epiphysis (ends) of bone ossify (secondary growth centers)
…….
What is the process of endochondral bone formation?
At birth and during the first 2 months of life, 2 parts of long bone remain cartilage ………
At maturity, cartilage plates completely ossified.
*ununited anconeal process common in large dogs: ossification not complete
What is intramembranous bone formation?
Occurs in some skull bones
Fibrous tissue membranes cover the brain of the fetus
As it matures, these membranes are ossified and form cranium
What is bone homeostasis?
Bone remodeling
Osteoclasts destroy bones (injured/damage)
Osteoblasts build bone.
Control mineral levels
What are the main minerals in bone building?
Calcium and phosphorus
Magnesium
Manganese
Copper
What vitamins are important in bone building?
Vitamin D
Vitamin A
What hormones are important in bone building?
- PTH (parathyroid hormone): increases calcium in the blood by: stimulating release of Ca from bone, inhibits Ca excretion by kidneys, stimulates absorption of Ca by the intestine
- Calcitriol (vitamin D): increases blood calcium by: inhibits Ca extretion by kidneys, stimulates Ca absorption in intestines
- Calcitonin: decreases blood calcium by: inhibiting release of Ca from bone, stimulate extretion of Ca by kidneys
What is growth hormone?
Responsible for overall growth of tissues in body, more in juvenile animals
Stimulates growth of epiphyseal cartilage
Stimulates calcium excretion by kidneys
Stimulates calcium absorption by intestine
What does insulin do in bone homeostasis?
Stimulate bone formation
What do sex hormones do in bone formation?
Stop longitudional growth by causing the epiphyseal plates to degenerate
Stimulate bone formation
Estrogen helps prevent osteoporosis
What do glucocorticoids (steroids: cortisol and alsosterone) do in bone formation?
Suppress calcium absorption
Decrease blood calcium concentration
Weakens bones
