Human Organ Systems
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What are the three functions of bone?
- Support (posture, alignment)
- Movement (provides sites of attachment for tendons and muscles)
- Mineral storage (Calcium and Phosphorus)
- Hematopoiesis (Site of blood formation)
- Energy storage (Yellow bone marrow/ stores triglycerides)
How do we know if a bone is a long bone?
If the length of the bone is greater than the width.
3 Structures of Long Bone
Explain the Diaphysis?
Composed of dense bone that surrounds central canal.
Where are the epiphyses located on the long bone?
At the primary (top) and distal (bottom) ends of the bone.
Explain the metaphyses
Includes the epiphyseal plates, and is where the long bone continues to grow during childhood and adolescents.
What does articular cartilage do?
Prevents bone from grinding against bone at a joint.
What does the periosteum do?
Surrounds the external bone surface (but not the cartilage)
What does the medullar cavity contain?
Yellow bone marrow
What is the function of the endosteum?
Lines the internal bone surface.
Bones are composed of:
- Inorganic salts
- ~Hydroxyapatite - Chemical crystals of calcium and phosphate that contribute to bone hardness
- Organic matrix
- ~Ground substance is composed from mixtures of proteins and polysaccharides and it contributes to bone flexibility
What are the four types of cells present in bone tissue?
- Osteogenic cells (stem cells)
- Osteoblasts (Bone forming cells that are foiund in all bone surfaces and removes calcium from the bone)
- Osteoclasts (Large multinucleated cells. Large number of lysosomes and mitochondria. Responsible for active erosion of bone surface and release of calcium into blood stream.)
- Osteocytes (Mature undividing osteoblasts embedded in matrix)
What is compact bone?
- Constitues 80% of the total bone mass
- Contains cylinder-shaped structural units called osteons, or Haversian systems
What are the four structures of osteon cell?
- Haversion Canal
What is cancellous bone oalso known as Spongy bone?
- Constitutes about 20% of total bone mass
- Consist of trabeculae (no osteons in trabecular bone)
- Nutrients delivered and waste products are removed through diffusion
What are the three arteries that supply blood flow to the bone?
- Periosteal arteries
- ~ Supply periosteum and outer layer of the diaphyses
- Nutrient artery
- ~ Enters bone through nutrient foramen (divides into distal and proximal branches). Supply the inner parts of compact bone of diaphysis and red marrow
- Metaphyseal and Epiphyseal arteries
- ~ Supply bone tissue of epiphyses and red marrow
What are the two types of bone formation?
Note: Bone development involves the replacement of pre-existing connective tissue with bone.
- Intramembranous ossification
- Endochondral ossification (formed in cartilage)
Where does intramembranous ossification occur?
- Within the connective tissue 'membranes'
- - example: flat bones of skull
What are the four steps of intreamembranous ossification?
- 1. Development of ossification center
- Mesenchymal cells -> osteogeic cells -> osteoblasts
- Osteoblasts secrete matrix material and collagenous fibrils
- 2. Calcification
- Deposition of calcium and other mineral salts
- 3. Formation of trabeculae
- The trabeculae appear and join in a network to form spongy bone
- 4. Development of periosteum
- Formation of compact bone
What are the 6 stpes of Endochondral ossification?
- 1. Development of a cartilage model
- Mesenchymal cells -> chondroblasts
- Chondroblasts secrete cartilage extracellular matrix
- 2. Growth of cartilage model
- Chondroblasts -> Chondrocytes
- Chondrocytes divide and form more of the extracellular matrix
- Interstitial Growth - growth in length
4. Development of medullary cavity
- 3. Primary ossification center forms
- Blood vessels enter the cartilage model
- Osteogenic cells differentiate into osteoblasts
- Endochondral ossification progresses from diaphysis to each epiphysis
- 5. Secondary ossification
- Starts when the branches of epiphyseal artery enter the epiphyses and proceeds outward from the center of epiphyses
6. Formation of articular cartilage and the epiphyseal plate
How do bones grow in lenght?
- Epiphyseal plate
- Resting cartilage cells
- Zone of proliferation
- Zone of hypertrophy
- Zone of calcification
What is bone remodeling?
- Dynamic process that involves bone resorption by osteoclasts and bone formation by osteoblasts
- Healthy bone: bone resorption = bone formation
- Osteoporosis: bone resorption > bone formation
What is the definition of a bone fracture?
A bone fracture is defined as a break in teh continuity of a bone
What are the common types of bone fractures? (5)
- Open fracture
- Closed fracture
- Comminuted fracture
- Greenstick fracture
- Impacted fracture
What are the four stages of bone repair?
- 1. Fracture hematoma forms
- Vascular damage initiates repair sequence and cloth forms
- 2. Fibrocartilaginous callus forms
- Collagen fibers are formed at the fracture site by fibroblasts
- 3. Bony callusforms
- Osteoblast produces specilalized bone tissue at the end of the broken bone
- 4. Bone remodels
- Osteoclast reabsorbs the dead bone and spongy bone is converted into compact bone
What percent of calcium does the skeletal tissue store?
How is calcium homeostasis maintained?
Calcium is mobilized and moves in and out of blood by the process of bone remodeling
In what 5 activities of the body is calcium essential?
- Bone formation and repair
- Blood clotting
- Enzymatic activity
- Transmission of nerve impulses
- Skeletal and cardiac muscles contractions
What two hormones are involved in calcium homeostasis maintenance?
- Parathyroid Hormone (Major)
- Stimulates bone resorption by osteoclasts
- Increases renal absorption of calcium from urine
- Stimulates the synthesis of vitamin D
- Produced in response to high calcium levels in the blood
- Stimulates bone formation by osteoblasts
- Inhibits bone resorption by osteoclasts
Where is the axial skeleton?
The axial skeleton lies on the longitudinal axis of the body.
What is the axial skeleton composed of?
- 80 bones
- Skull = 22 bones (8 cranial and 14 facial)
- Auditory ossicles
- Hyoid bone (1)
- Vertebral column = 26 bones
- Cervical, Thoracic, Lumbar, Sacral, Coccyx
- Thoracic cage = 25 bones
- Ribs and sternm
What are the five different types of bones?
- Long (length of bone > width)Short (ex. wrist ; nearly = in length and witdth)Flat (Composed of two plates of flat bone; middle layer = spongy bone..ex. cranial bones)
- Irregular (Variable bones that cannot be grouped in any other categories)Sesamoid (sesame seed shaped; develop in tendons and ligaments)
How does bone surface marking occur?
Bone surface marking develops through various forces, most of which are not present at birth)
What is the purpose of bone depressions and openings?
Allow for the passage of blood vessels, nerves, ligaments and tendons, as well as to form joints.
What is the purpose of cranial bones?
The cranial bones form the cranium (braincase) which is used for protection of the brain.
Note: all eight cranial bones are held together by fixed joints called sutures.
What are the eight cranail bones?
- Frontal bone
- Parietal bones (2 bones)
- Temporal bones (2 bones)
- Occipital bones
- Sphenoid bone
- Ethmoid bone
What is the purpose of the frontal bone?
- Forms the anterior part of the braincase and upper eye sockets
- Contains the frontal sinuses
- Function: protect frontal lobe of the brain
What is the purpose of the parietal bones?
- Forms part of the superior and lateral surfaces of the braincase
- Forms articulations with the other parietal bone, as well as occipital, temporal, frontal and sphenoid bones
What is the purpose of the temporal bones?
- Forms the inferior lateral part of the cranium
- Forms a part of the cranial floor
- Contain the inner and middle ears
What is the purpose of the occipital bone?
- Forms the posterior surfaces and most of the base of the cranium
- Forms immovable joint with parietal, temporal and sphenoid bones
- Forms a movable joint with the first cervical vertebrae (atlas)
- Opening called foramen magnum allows the spinal cord from cranium into vertebral foramen
What is the purpose of the sphenoid bone?
- Located in the central portion of the cranial floor
- Provides the base for the cranium, supporting the brain
- Anchors the frontal, parietal, occipital and ethmoid bones
- Contains sphenoid sinuses
- Pterygoid processes serves as an attachment site for jaw muscles
- Hypophyseal fossa contains pituitary gland
- A bat-shaped bone
What is the purpose of the ethmoid bone?
- Forms the anterior portion of the floor of the cranial cavity
- Forms the roof of nasal cavity
- Articulates with frontal bone and few bones of the face
- Roof of a nasal cavity
- Contains the cribriform plate, a sieve-like structure, that allows olfactory nerves to extend from olfactory bulb of the brain into the mucus membrane of the nasal cavity
What is the purpose of the facial bones?
Facial Bones protect the entrances to the digestive and respiratory tract, and the sensory organs
What are the fourteen facial bones?
- Maxilla (upper jaw)
- Mandible (lower jaw)
- Zygomatic bone
- Nasal bone
- Lacrimal bone
- Palatine bone
- Inferior nasal conchae
- Vomer bone
What is the purpose of the maxillary bone?
- Support upper teeth
- Forms upper jaw and hard palatte
- Alveolar processes hold upper teeth
What is the purpose of the mandible bone?
- Together with temporal bone forms the only moveable joint of the skull (Temporo-mandibular joint)
- The largest and strongest bone of the face
What is the purpose of the zygomatic bone?
- Shapes the cheek
- Forms the outer margin of the orbit
What is the purpose of the lacrimal bone?
- Small, paired bones that form the anterior portion of the medial wall of the orbit
- Forms the nasal cavity
- Articulates with the maxilla, frontal and ethmoid bones
What is the purpose of the pallatine bones?
- Two bones that form a posterior part of the hard plate
- Articulate with the maxillae and sphenoid bone
- A cleft plate results if the palantine bones do not completely fuse during development
What is the prupose of the inferior nasal conchae (turbinates)?
- Project into nasal cavity
- Form the nasal meati
- Articulates with ethmoid, lacrimal, maxillary and palatine bones
What is the purpose of the vomer bone?
Forms the posterior portion of nasal septum
What is the hyoid bone?
- The only bone of the skeleton that is not directly attached to any other bony structure
- Suspended by the throat muscles
- Lies below the tongue
What do the eye orbits contain?
Contain eyes, eye muscles, lacrimal apparatus as well as blood vessels and nerves
True or false. The vertebral column is the central axis of the skeleton.
What are the five regions of the vertebral column?
- Cervical vertebrae
- Thoracic vertebrae
- Lumbar vertebrae
- In adults results from the fusion of 5 separate vertebrae
- In adults, results from the fusion of 4-5 separate vertebrae
What is the purpose of the normal curves of the vertebral column, and what are the two types of curves?
Normal curves give the spine strength for support of the body and assist in balance.
- 2 types:
- Primary Curves
- Secondary Curves
What are the atlas and axis vertebrae?
- First cervical vertebra
- Allows for the nodding movement “yes”
- Second cervical vertebra
- Allows for the pivotal movement “no”
What are the 2 functions of the vertebral column?
- Protects the spinal cord
- Site for muscle attachment
What are the 3 parts of the vertebral column?
- Vertebral body
- Vertebral arch
- Vertebral articular processes
Where are the invertebral discs located, and what are their functions?
- Positioned between adjacent vertebrae
- Annulus fibrosus
- Nucleus pulposus
- Absorb vertical shock
- Allows movement of vertebral column
What bones form the thorax?
Ribs, vertebral column, and sternum
What are the 12 pairs of ribs and where are they attached?
- Ribs 1-7 directly attached to the sternum by costal cartilage
- Ribs 8-10 are indirectly attached to the sternum by costal cartilage
- Ribs 11 and 12 are floating ribs
Where is the sternum (breastbone) located?
In the middle of the chest
What are the 3 parts of the sternum?
- Articulates with the clavicle and first rib
- Middle, blade part
- Xiphoid process
- Cartilaginous lower tip that ossifies during adult life
What is the appendicular skeleton composed of?
- 126 bones
- Pectoral (shoulder) girdle
- Upper appendages (arms and hands)
- Pelvic (hip) girdle
- Lower appendages (legs and feet)
What bones make up the upper extremity of the appendicular skeleton?
The shoulder girdle, upper and lower parts of the arm, wrist and hand
What is the purpose anf function of the pectoral (shoulder) girdle?
- Consist of the scapula and clavicle
- Clavicle articulates with sternum (sternoclavicular joint)
- Clavicle articulates with the acromion processes of scapula (acromioclavicular joint)
- Scapula is held in place by muscles only
- Gives each shoulder joint greater range of motion
What is the humerus and what is its function?
- Long bone of the upper arm
- Articulates proximally with the glenoid fossa of the scapula
- Greater and lesser tubercles-sites of muscle attachment
- Articulates distally with the radius and ulna (elbow joint)
- Capitulum-articulation with head of radius
- Trochlea-articulation with ulna
- Medial and lateral epicondyles-sites of forearm attachment
Where is the ulna located and what is its function?
- Position on the medial side of the forearm Articulates proximally with the humerus (trochlear notch) and radius (radial notch)
- Articulates distally with fibrocartilaginous disk
Where is the radius located and what is its function?
- The long bone located on the thumb side of the forearm
- Articulates proximally with the capitulum of the humerus and radial notch of ulna
- Articulates distally with the scapoid and lunate carpals and with the head of ulna
The wrist is made up of the carpal bones. How are they lined up and what is their function?
Joint between the radius and carpal bones allows for the wrist and hand movement
- Two rows of four short bones
- Proximal row: pisiform, triquetrum, lunate and scaphoid
- Distal row: hamate, capitate, trapezoid and trapezium
What is the purpose of the metacarpal bones?
- Framework of the hands
- Heads of metacarpals articulates with the phalanges
- When making a fist the distal end of the metacarpals protrude to form the knuckles.
Are the phalanges (finger bones) considered long bones?
What are the three bones found in each finger?
- The thumb has only two bones
What bones make the lower extremity of the appendicular skeleton?
Composed of the bones of the hip, thigh, lower part of the leg, ankle and foot
What are the bones of the pelvic girdle?
Composed of the sacrum and coxal bones bound tightly by strong ligaments
What are the 3 parts of the coxal bones?
- Each coxal bone is composed of ilium, ischium and pubis
- Fused after birth at acetabulum
Where on the coxal bone are the ilium, ischium, and pubis located?
- Largest and uppermost of three bones
- Strongest and lowermost of three bones
- Medial anterior section
What is the femur and its function?
- Longest and heaviest bone in the body
- Head articulates with acetubulum
What is the patella (kneecap) and its function?
- Largest sesamoid bone in the body
- Located in the tendon of the quadriceps femoris muscle
With what two bones does the tibia articulate with?
- Articulates proximally with femur (knee joint)
- Articulates distally with fibula and talus
Whatt is the tibia?
- Medial leg bone
- Larger and stronger of the two leg bones
- Weight bearing bone
What is the fibula and where is it located?
- Smaller of the two leg bones
- Located more laterally and deeply of the two bones
- At the proximal end articulates with lateral condyle of tibia
- Not a part of a knee joint
What is the form and function of the foot?
- Similar to hand but adapt for supporting the weight
- Foot bones are held together to form a spring arches
What are the two types of foot arches?
- Longitudinal arch
- Medial longitudinal arch
- Lateral longitudinal arch
- Transverse arch
- Located across midfoot region
How are the arches of the foot maintained?
- Ligaments and leg muscle tendons hold the foot firmly in their arched position
- Flatfeet (fallen arches)- condition in which the arches flatten
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