skeletal system 1 Flashcards
The primary function for the skeletal system is what?
For supporting the body and protecting vital organs
How many bones are we born with? How much is left when we age?
270
206 named bones
What are bones made up of?
Bones are made up of a complex arrangement of inorganic minerals and a variety of tissues including bone, bone marrow, nerves, blood vessels, endothelial, and cartilage
What are the functions of bones?
- Protection - of organs (skull protects the brain, ribs protects the heart, etc)
- Support and framework for the human body
- Movement - by providing attachment points for muscles
- pH balance - of the blood by absorbing or releasing bone minerals
- Hematopoiesis - (blood production) in blood marrow
- Fat storage - in yellow bone marrow
- Sound transduction - through small bones located in the ear canal
- Storage of growth factor in bone matrix
- Removal of heavy metals or foreign chemicals - to detoxify blood and release slowly for excretion
- Mineral storage - of calcium and phosphorous
- Production of hormones - such as ostocalcin
What are bone minerals mostly made of?
Calcium and phosphorous
Bone mineral is created by what? And it allows what?
Osteoblasts
Allows bones to withstand large amounts of compressional force
What is the other major component of bone matrix?
Organic collagen, which is a protein that gives bone the ability to withstand stretching forces
What are the major cells that contribute to building and breaking down bone matrix and bone structure?
Osteoblasts, osteocytes, and osteoclasts
Osteoblasts are responsible for what?
Responsible for creating bone matrix, and therefore building bone
When does osteoblasts become osteocytes?
Once osteoblasts have become trapped in the bone matrix they have created, they become osteocytes
What is the function of osteocytes?
Maintain the bone matrix and calcium homeostasis
Osteocyte, a cell that lies within the substance of fully formed bone. It occupies a small chamber called a lacuna, which is contained in the calcified matrix of bone. Osteocytes derive from osteoblasts, or bone-forming cells, and are essentially osteoblasts surrounded by the products they secreted.
Where are osteocytes located?
Lacunae
What are osteoclasts?
Large cells that are capable of reabsorbing bone minerals, and therefore remodeling bone structure
They also remove minerals to the bloodstream for a variety of bodily functions, such as muscle contraction
Bone matrix can be arranged into what classifications?
- Compact bone
2. Trabecular bone
Define compact bone
Also known as dense or cortical bone, is extremely hard and compact with very little space
Bone mineral in compact bone is arranged into tight circles called osteons, with nerves and blood vessels passing through the center. Compact bone accts for 80% of the total bone mass
Define trabecular bone
Also known as spongy or cancellous bone, is porous and more like a network that allows nerves, blood vessels, and bone marrow to easily fill trabecular bone
Stress on trabecular bone causes it to create new and stronger networks, making it extremely adaptable
Accts for 20% of the total bone mass, it has a greater surface area than compact bone
What are the five main types of bone based on their shape?
- Long bones - bones that are longer than they are wide and made up of primarily compact bone (e.g. arm bones, leg bones, and phalanges)
- Short bones - cube-shaped with a thin layer of compact bone (e.g. wrist and ankle bones)
- Sesamoid bones - bones embedded in tendons. (e.g. patella and pisiform)
- Flat bones - thin and curved with parallel layers of compact bone. (e.g. sternum and bones of the skull)
- Irregular bones - bones that do no fit in any of the other categories. (e.g. vertebra and bones of the sinus)
What does collagen fibers allow bones to do?
The presence of collagen fibers allow bone to endure stretching forces
What does mineral salts allow bones to do?
Allow bones to endure compression forces
How is the bone construction similar to reinforced concrete?
Similar in that steel rebar allows concrete to resist strecthing forces, while the cement resists compression
Bone structure is somewhat similar to reinforced concrete that contains structural metal reinforcement rods or bars. These metal reinforcements are commonly called rebar. Protein strands make up the rebar of bone. Calcium and phosphorus mineral crystals deposited around the protein strands are somewhat like the concrete poured around the rebar in reinforced concrete. The protein strands provide the tensile strength that holds everything together and the minerals provide the solid structure. If bones were made only of protein, they would be too flexible. If bones were made solely from minerals, the skeleton would be too brittle.
What is the function of osteons?
Allows the bone to resist greater amounts of force
The bone construction does not resist what?
Does not tend to resist twisting forces, and in fact is the primary cause of bone fractures
What are the two main components of extracellular matrix?
Mineral salts and collagen
What types of force do collagen and bone mineral resist?
Bone mineral resist compression forces
Collagen fibers resist tension forces
What chemicals make up the organic portion of the bone extracellular matrix?
Made up of proteoglycans, water, minerals, and fibrous proteins
What chemicals make up the inorganic portion of the bone extracellular matrix?
Consists of hydroxapatites or minerals salts, primarily calcium phosphate
What portion of the bone extracellular matrix is most responsible for bone flexibility?
Collagen contribute to the flexibility and tensile strength of the bone
What portion of the bone extracellular matrix is most responsible for bone hardness?
The mineral salts are responsible for hardness
What passes through the Haversian canal?
The Haversian canal contains its own blood vessels, which supply nutrients to the bone cells of the osteon and its own nerve fibers
What is created in red bone marrow?
It produces red blood cells, white blood cells, and platelets
Where are the blood vessels found in compact bone?
In the Haversian canal
Where are the blood vessels found in spongy bone?
In between the trabulcae
number of axial bones
80
number of skull bones
29
Cranium bones
Frontal Parietal Temporal Occipital Sphenoid Ethmoid
forehead, eyebrows, superior eye orbit
Frontal bone
superior and lateral walls of cranium
parietal bones
parts of temporal bones
external acoustic meatus styloid process zygomatic process mastoid process internal acoustic meatus
canal that leads to eardrum and middle ear
external acoustic meatus
most posterior bone of cranium
occipital bone
hole at the base of the skull where spinal cord enters skull
foramen magnum
Types of bone fractures
Closed (simple) fracture: break that does not penetrate the skin
Open (compound) fracture: broken bone penetrates through the skin
Stages in healing bone fracture
Hematoma (blood-filled swelling) is formed
Fibrocartilage callus forms
Cartilage matrix, bony matrix, collagen fibers splint the broken bone
Bony callus replaces the fibrocartilage callus
Osteoblasts and osteoclasts migrate in
Bone remodeling occurs in response to mechanical stresses
Skull and associated bones include
cranium 8, face 14 Auditory ossicles 6, hyoid 1
Thoracic cage includes
sternum 1 , ribs 24 bones
Vertebral column includes
Vertrebrae, 24, Sacrum 1, Coccyx 1
Pectoral girdle (4) includes
Clavicle 2, Scapula 2,
Upper limbs include (60)
Humerus (2), Radius (2), Ulna (2), Carpal bones (16), Metacarpal bones (10), Phalanges (proximal, middle, distal 28 bones total)
Pelvic girdle (2) includes
Hip bone (Coxal bone 2)
Lower limbs (60)
femur (2), Patella (2), Tibia (2), Fibula (2), Tarsal bones (14), metatarsal bones (10), phalanges (28)
The axial skeleton is divided into
Divided into three parts Skull Vertebral column Bony thorax Forms the longitudinal axis of the body
The skull is made up of
Two sets of bones
Cranial (8) – encloses and protects the brain
Facial bones (14) – hold the eyes, facial muscles in place
Bones are joined by sutures
Only the mandible is attached by a freely movable joint
cranium is composed of
Composed of 8 large flat bones 1. Frontal bone 2. Occipital bone 3. Ethmoid bone 4. Sphenoid bone 5–6. Parietal bones (pair) 7–8. Temporal bones (pair)
Facial bones
14 bones in total – 12 are pairs, two are single Key facial bones: Maxillae 2 bones fused together, forms the upper jaw Mandible Single bone, forms the lower jaw Nasal Forms the nose
There are 14 facial bones. All are paired except for the single mandible and vomer. 1–2. Maxillae (upper jaw) 3–4. Zygomatics 5–6. Palatines 7–8. Nasals (nose) 9–10. Lacrimals 11–12. Inferior nasal conchae 13. Mandible (lower jaw) 14. Vomer
Paranasal sinuses
Hollow portions of bones surrounding the nasal cavity
Associated bones of the skull
Hyoid bone
Attachment site for muscles of larynx, tongue, pharynx
Aids in swallowing and speech
Auditory ossicles
Enclosed in temporal bone
Play a role in conducting vibrations to inner ear
The fetal skull _______
The fetal skull is large compared to the infant’s total body length
Fetal skull is 1/4 body length compared to adult skull which is 1/8 body length
Fontanels
Fontanels - fibrous membranes connecting the cranial bones
Aids with delivery, Allows the brain to grow, Convert to bone within 24 months after birth, Can feel pulse over the fontanels, Largest is the diamond shaped one called the anterior fontanel, The smaller is triangular shaped and called the posterior fontanel
The vertebral column
26 bones (24 vertebrae, sacrum, coccyx) separated by discs
Provides column of support – transfers body’s weight to lower limbs
Protects spinal cord
Maintains upright position
Vertebral regions
Cervical (7 vertebrae – C1 to C7) Thoracic (12 vertebrae – T1 to T12) Lumbar (5 vertebrae – L1 to L5) Sacral (5 fused vertebrae – S1 to S5) Coccygeal (3 – 5 fused vertebrae)
Vertebral Canal
Encloses spinal cord
Spaces between successive vertebrae – intervertebral foramina
Passageway for nerves and blood vessels
Normal curves of the vertebral column
The spine has a normal curvature
Primary curvatures are the “C”-shaped spinal curvatures of the thoracic and sacral regions - present from birth
Secondary curvatures are the “S”-shaped spinal curvatures of the cervical and lumbar regions - develop after birth
Intevertebral discs
Each single vertebrae is separated by pad of flexible fibrocartilage called a disc
Disc
Cushion / shock absorption
Spinal flexibility
Composed primarily of water (90%)
Reduced water content with age
The bony thorax
Forms a cage to protect major organs Sternum Manubrium Body Xiphoid process Ribs True ribs (pairs 1–7) False ribs (pairs 8–12) Floating ribs (pairs 11–12) Intercostal spaces (ICS) are between the ribs Thoracic vertebrae - attachment for the ribs
The appendicular skeleton is composed off
Composed of 126 bones subdivided into 3 parts:
Pectoral girdle
Pelvic girdle
Limbs (appendages)
The pectoral girdle is composed of
Made of two bones which connect upper limbs to trunk
Clavicle
Scapula
These bones allow the upper limb to have exceptionally free movement at expense of stability
