W10 The Skeletal System Flashcards
Bones and Bone tissue
What are the major functions of bones and bone tissue? (5)
- Support
▪ Provides a framework, and provides attachment points for muscle and tendons; ligaments connect bone to bone - Protection
▪ Containment of valuable organs - Assistance in movement
▪ Muscle provides the power; skeleton provides the movement; tendons connect - Mineral storage and release
▪ Blood/bone Calcium and phosphorous levels maintained - Blood cell production
▪ Red marrow present in certain bones use haematopoiesis to produce RBCs, white cells, platelets
Axial and Appendicular systems:
How many bones are in each?
Axial = along the axis
~80 Bones
Essentially houses the vital parts of the
body
Appendicular = appendage
~126 Bones
- locomotion
The Skeletal System:
What is included?
What does cartilage protect?
What do tendons connect?
What do ligaments connect?
- Axial Bones and Appendicular bones
- Associated connective tissues
- Cartilage, tendons, and ligaments
Cartilage –protects joints,
Tendons –connects muscles to bone
Ligaments –connects bones to bones
What is the function of bones?
What are the types of bone? (5)
Function: Support and articulation
- Sesamoid ( lie within tendons)
- Short bones- wider than they are long (found in ankles and wrists)
- Flat bones e.g. skull, ribs
- Long bones- longer than they are wide
- Irregular bones
What are the 2 structures of bones?
Compact bone
Cancellous (spongy) bone
What is compact bone? (5)
What does it consist of?
Where is it found?
- Dense and solid in appearance
- Protection and strength
- Repeating circular units
- Consists of Osteons
- Found in long bones
What is Cancellous (spongy) bone/trabecular bone?
- Characterised by open space partially filled with needle-like structures = trabeculae
- Strength without weight (weighs way less than compact)
Short, flat, and irregular bones:
What are the inner and outer portions like?
Inner portion = cancellous /spongy bone
Outer portion = covered on the outside with compact bone
Anatomy of a long bone (need to know)
- Diaphysis/Shaft
- Hollow
- Outside compact bone
- Inner = spongy- support without weight
- Epiphyses (plural)
- Both ends
- Cancellous / spongy
What is bone matrix composed of? (2)
- Inorganic salts
Hydroxyapatite :
- Chemical crystals of Calcium and Phosphate
-Compression strength - Organic matrix
- Composite of collagen (rope-like) fibres and proteoglycans
-Flexible strength
Bone- Relatively small number of bone cells in a matrix
What is Bone Marrow?
What is it the site of?
- A specialised type of soft, diffuse connective tissue; called myeloid tissue
- Site for the production of blood cells- Haematopoiesis
Where is bone marrow found?
- Found in medullary cavities of long bones and in the spaces of spongy bone
What are the 2 types of bone marrow?
Where are they found?
Red marrow and Yellow marrow
Red
-Found in virtually all bones in an infant’s or child’s body
- Produce red blood cells
Yellow
- As an individual ages, red marrow is replaced by yellow marrow
- Marrow cells become saturated with fat and are no longer active in blood cell production
In which bones does haematopoiesis take place?
Cranium
Ribs
Skulls
Pelvis
Ends of long bones (epiphyses)
What are the major bone cells? (4)
- Progenitor cells
- Osteoblasts
- Osteocytes
- Osteoclasts
What are mature osteoblasts called?
Osteocytes
What are osteoblasts?
- Bone-forming cells found in all bone surfaces
- Ossification/osteogenesis (lay down bone)
- Secretes organic component –collagen
- Produce vesicles: release Ca2+ and phosphate ions which contribute to hydroxyapatite formation
- Osteoid
What are osteocytes?
- Differentiated mature non-dividing osteoblasts
- Trapped in lacuna (calcified matrix) and serve mainly as mechanosensors/ mineral homeostasis
*They sense what’s happening in bone
What are osteoclasts?
- Giant cells
- Resorb bone through dissolving mineral and
breaking down collagen - The “macrophages” of bone
- (develop from blood cells called monocytes and macrophages)
*They break down bone
What happens during Bone Remodelling? (6)
- Removal of existing bone by osteoclasts and the deposition of new bone by osteoblasts
- Growth
- Changes in bone shape
- The adjustment of bone to stress
- Bone repair
- Calcium ion regulation in the body fluids
How are calcium levels regulated?
- Skeletal system: storehouse for about 98% of body calcium reserves
- Calcium moves into and out of blood
- Bone formation: osteoblasts remove calcium
from blood (and lay it down in bone) - Bone breakdown: osteoclasts release calcium into blood
- Calcium homeostasis : hormonal control
- Parathyroid hormone (PTH)* Primary regulator
- Stimulates osteoclasts to breakdown bone matrix
- Increases kidney absorption of calcium from urine
- Increases blood calcium levels
- Vitamin D * Increases calcium absorption from the small intestine
- Increases blood calcium levels
- Calcitonin* Hormone produced in the thyroid gland
- Stimulates bone deposition by osteoblasts
- Inhibits osteoclast activity
- decreases blood calcium levels
What are the 3 hormones that are important in calcium homeostasis?
- Parathyroid hormone (PTH) (inc blood levels)
- Vitamin D (inc blood levels)
- Calcitonin (dec blood levels)
How does Parathyroid (PTH) hormone help regulate calcium homeostasis?
- Primary regulator
- Stimulates osteoclasts to breakdown bone matrix
- Increases kidney absorption of calcium from urine
- Increases blood calcium levels
How does Vitamin D help regulate calcium homeostasis?
- Increases calcium absorption from the small intestine
- Increases blood calcium levels
How does Calcitonin help regulate calcium homeostasis?
- Hormone produced in the thyroid gland
- Stimulates bone deposition by osteoblasts
- Inhibits osteoclast activity
- Decreases blood calcium levels
What changes occur to the skeleton during ageing?
What bone is lost first?
What decreases?
- Decreased collagen makes bones more brittle
- Cancellous bone lost first
- Decrease in no of trabeculae
- Followed by compact bone
- Incomplete remodelling
What is osteoporosis?
- Bone resorption exceeds bone deposition.
- First Line Therapy: oral bisphosphonates eg alendronic acid and risedronate sodium
- Induce osteoclast apoptosis (death) and suppress bone resorption
Bones in the wrist are categorised as what?
Short bones
Long bones grow in length due to activity in the ____?
epiphyseal plate
perichondrium
periosteum
medullary cavity
epiphyseal plate
Which of the following are capable of undergoing Mitosis?
-Osteoblasts
-Osteocytes
-Osteoclasts
-Progenitor cells
Progenitor cells
Which of the following lay down bone?
-Osteoblasts
-Osteocytes
-Osteoclasts
-Progenitor cells
Osteoblasts
The major bone cells produce in which order?
Progenitor- Osteoblast- Osteocyte
