SKELETAL SYSTEM Flashcards
Skeletal system
Body system composed of bones, cartilage, and ligaments of body that supports and give shape to body and body structures
Bone
Hard, dense connective tissue that forms most of adult skeleton
Cartilage
Semi-rigid connective tissue that provides flexibility and smooth surfaces found in areas where bones move
Functions of skeletal system (6)
- Support
- Movement
- Protection
- Mineral storage
- Energy storage
- Hematopoiesis
Support
Bones and cartilage support the rest of the body
Movement
Bones facilitate movement by serving as points of attachment for muscles and they also act as levers
Protection
Bones protect internal organs from injury by covering/surrounding them (eg. Ribs protect lungs and heart, vertebrae protect spinal cord, skull protect brain)
Mineral storage
Bone matrix acts as reservoir for some minerals which is important to functioning of body like calcium and phosphorus; these minerals can be released back into bloodstream to maintain levels needed to support physiological processes
Energy storage
Bone marrow in softer connective tissue that fills interior of bone contains yellow bone marrow which has adipose tissue and the triglycerides stored here serve as energy source
Hematopoiesis
Red bone marrow is where hematopoiesis is where production of blood cells occur; RBC, WBC and platelets are all produced in red marrow
How many bones are in adult skeleton and how many categories
206 bones divided into 5 broad categories based on shape
Bone classification (5):
- Long
- Short
- Flat
- Irregular
- Sesamoid
Long (8)
Cylinder like shape, functions in leverage (eg. Tibia, fibula, metatarsals, humerus, ulna, radius, metacarpals, phalanges)
Short (2)
Cube like shape equal in width length thickness, functions in providing stability and support while allowing motion (eg. Carpals, tarsals)
Flat (4)
Thin and curved, functions in points of attachment for muscles and protects internal organs (eg. Sternum, rib, scapulae, cranial bone)
Irregular
Complex shape, functions in protecting internal organs (eg. Vertebrae, facial bone)
Sesamoid
Small and round embedded in tendons, functions in protecting tendons from compressive forces (eg. Patallae)
Long bone
Contains two parts (diaphysis and epiphysis)
Diaphysis structure
Is a tubular shaft that runs between proximal and distal ends of bone and contains a hollow region called medullary cavity which is filled with yellow marrow. Walls are composed of dense and hard compact bone
Epiphysis structure
Wider section at each end of bone filled with spongy bone with spaces filled of red marrow
Metaphysis
Where the epiphysis and diaphysis meet that contains epiphyseal plate (layer of hyaline cartilage in a growing bone)
Epiphyseal line
Serves as indicator of boundary between epiphysis and diaphysis. Epiphyseal plate becomes epiphyseal line when bone as matured (stops growing) in early adulthood and cartilage is replaced by osseous tissue
Endosteum
Delicate membranous lining in medullary cavity where bone growth, repair, and remodelling occur
Periosteum
Fibrous membrane covering the outer surface of bone (except where epiphyses meet) containing blood vessels, nerves, and lymphatic vessels that nourish compact bone
Articular cartilage
Thin layer of cartilage that covers epiphyses to reduce friction and absorb shock
Spongy bone and compact bone
Two layers of compact bone and interior spongy bone work together to protect internal organs. If the outer layer of a cranial bone fractures, the brain is still protected by the inner layer
Bone cells structure
Relatively small number of cells that are entrenched in a matrix of collagen fibers
Hydroxyapatite
Inorganic salt crystals made of calcium phosphate (hydroxyapatite) that adhere to collagen and gives bones their hardness and strength
Collagen fiber function in bones
Impart flexibility so that bones are not brittle
4 types of bone cells:
- Osteocyte
- Osteoblast
- Osteogenic cell
- Osteoclast
Osteoblast
Responsible for forming new bones found in growing portions of bone, including periosteum and endosteum; Secretes organic compounds of matrix
Function of osteoblasts that don’t divide
Synthesize and secrete the collagen matrix and calcium salts
Osteocyte
A mature and the most common bone cell that results from when a trapped osteoblast changes in structure and becomes osteocyte; Maintains bone matrix and lives in lacunae
Lacuna
Spaces where osteocytes are found and surrounded by bone matrix
Osteogenic cell
Undifferentiated cells that develop into osteoblasts
Osteoclast
Functions in bone resorption and found on bone surfaces, multinucleated, and originate from two types of white blood cells and not from osteogenic cells; Secrete acid and enzymes to dissolve bone matrix
Spongy bone
Contains open spaces and supports shifts in weight distribution. It contains osteocytes housed in lacunae arranged in a lattice network of matrix spikes called trabeculae
Compact bone
Dense and can withstand compressive forces; found deep in periosteum and in diaphyses
Osteon
Structural unit of compact bone, composed of concentric rings of calcified matrix called lamellae
Central canal
Found in each center of osteon that contains blood vessels, nerves, and lymphatic vessels that branch off at right angles through the perforating canal
Canaliculi
Connect with canaliculi of other lacunae and eventually with central canal which allows nutrients to be transported to the osteocytes and wastes to be removed from them
Trabeculae
Refers to the lattice like network of matrix spikes of lacunae and osteocytes in spongy bone providing strength to bone and the spaces in between makes bones lighter so that muscles can move them more easily. Some also contain red marrow
Nutrient arteries
Pass through nutrient foramen (small opening in diaphysis) that nourish the spongy bone and medullary cavity
How are osteocytes in spongy bone nourished
Blood vessels of the periosteum that penetrate spongy bone and blood that circulate in marrow cavities
Nerve supply to bone
Nerves also follow the same path into the bone through nutrient foramen and concentrate into more metabolically active regions
Skeleton in embryonic early stages
Consists of only fibrous membranes and hyaline cartilage. By week 6 or 7 of development, ossification (formation of bones begins)
2 pathways of ossification:
- Intramembranous ossification
- Endochondral ossification
Cartilage templates (2)
- Bone is a replacement tissue; uses model of cartilage on which to lay down matrix
- Framework of flexible semi solid cartilage is laid down to determine where born will form during fetal development –> replaced with bone as fetus is born
Intramembranous ossification
Occurs in flat bones of face, most cranial bones and clavicles
7 Steps of intramembranous ossification -
- Mesenchymal cells differentiate into specialized cells (osteogenic cells and capillary forming cells)
- Osteoblasts form clusters called ossification centers
- Osteoblasts secrete osteoid which calcifies and traps osteoblasts and transforming them into osteocytes
- Surrounding osteogenic cells differentiate into new osteoblasts
- Osteoid secretion around capillaries forms trabecular matrix, and osteoblasts on surface become periosteum
- Periosteum forms protective layer of compact bone
- Trabecular bone crowds nearby blood vessels which condense into red marrow
Endochondral ossification
Occurs at bones on base of the skull long bones and involves bone development by replacing hyaline cartilage template and takes longer than intramembranous ossification
9 steps of endochondral ossification:
- Mesenchymal cells differentiate into chondrocytes that form cartilaginous skeletal precursor
- Perichondrium appears and chondrocytes in center grow in size
- Matrix calcifies, leading to chondrocyte death and disintegration of surrounding cartilage
- Blood vessels invade spaces, enlarging them and carrying osteogenic cells
- Space combines to form medullary cavity and capillaries penetrate cartilage
- Perichondrium transforms into periosteum and periosteal collar of compact bone forms around cartilage
- Primary ossification center forms deep in periosteal collar
- Similar events occur in secondary ossification centers in epiphyseal regions
- Cartilage remains at joint surfaces as articular cartilage and between diaphysis and epiphysis as growth plate responsible for bone lengthening
Epiphyseal plate
Area of growth in long bone and is a layer of hyaline cartilage where ossification occurs in immature bones (longitudinal)
Bone growth on epiphyseal side of epiphyseal plate
Cartilage is formed
Bone growth on diaphyseal side of epiphyseal plate
Cartilage is ossified and diaphysis grows in length
Growth plate zones (4)
- Reserve zone
- Proliferative zone
- Maturation and hypertrophy zone
- Calcified zone
Reserve zone
Closest to epiphysis consisting of resting chondrocytes that anchor the growth plate to bone
Chondrocyte function in reserve zone
Do not participate in bone growth but secure the growth plate to the osseous tissue of epiphysis
Proliferative zone
Chondrocytes undergo rapid cell division leading to formation of new chondrocytes
Zone of maturation and hypertrophy
Chondrocytes are older and larger and contribute to lengthening of bones
Cause of longitudinal growth of bone
Result of cell division in the proliferative zone and the maturation of cells in zone of maturation and hypertrophy
Calcified zone
Cartilage matrix becomes calcified and chondrocytes die. Serves as bridge for invasion of blood vessels and transformation of cartilage into bone
When does longitudinal growth stop
When the chondrocytes in the epiphyseal plate cause proliferation and bone replaces the cartilage; bones will continue to grow in length until early adulthood
Appositional growth
Bone growth in diameter; bones increase in diameter as they grow in length and even after growth in length ceases
Bone modelling
Process of shaping and forming bone during growth and development
Bone remodeling
Refers to the lifelong process of continuous renewal and maintenance of old or damaged bones
Fracture
Broken bone. Fractures will heal whether or not a physician resets it in its anatomical position and if it not reset correctly, the healing process will keep the bone in its deformed position
Open (compound) fracture
Fracture in which at least one end of the broken bone tears through the skin; carries high risk of infection
Closed (simple) fracture
Fracture in which the skin remains intact
Greenstick fracture
Partial fracture in which only one side of the bone is broken
Greenstick fracture
Comminuted fracture
Bone that is broken in two or more places causing many small pieces
2 major divisions of skeleton:
- Axial skeleton
- Appendicular skeleton
Axial skeleton function (3):
- Forms vertical, central axis of body
- Includes all bones of head, neck, chest, and back to
- Protects the brain, spinal cord, heart and lungs. It also serves as attachment site for muscles that move the head, neck, and back for muscles to act across shoulder and hip joints
Bones of axial skeleton region (5)
- 80 bones total in adult
- Skull (22 bones)
- Vertebral column (24 bones)
- Sacrum, coccyx, thoracic cage (25 bones)
- Hyoid and the 6 ear ossicles associated with head
Skull function
Supports face and protects brain
Divisions of skull
Facial bones and brain case
What is the only moveable bone in the skull
The 22nd bone is the mandible (lower jaw) and is the only moveable in the skull
Are the other bones in the skull moveable
No 21 are immobile so only the 22nd
Fontanelle
Areas of dense connective tissue that separate the bones of the brain case as they grow
Importance of fontanelle in infant
They are soft spots o n an infants head that are important during birth because they allow the skull to change shape as it squeezes through the birth canal
Anterior view of skull (3):
- Consists of facial bones that provide bony support for eyes and facial structures
- View is dominated by openings of the orbits and nasal cavity
- Upper and lower jaws with teeth
Important bones present anterior view of skull (5):
- Frontal bone
- Parietal bone
- Temporal bone
- Maxilla
- Mandible
Lateral view of the skull
View is dominated by the large rounded brain case above the lower jaws with teeth
Important bones present in lateral view of the skull (6):
- Frontal bone
- Parietal bone
- Temporal bone
- Occipital bone
- Maxilla
- Mandible
Posterior view of skull
View is dominated by the posterior rounded brain case as well as the posterior faces of the maxilla and mandible; showing attachment site for muscles and joints that support skull
Important bones present in the posterior view of the skull (4):
- Parietal bone
- Temporal bone
- Occipital bone
- External occipital protuberance
How many bones are found associated with head
7
Ossicles
3 inner ear bones associated with the head; malleus, incus, stapes that function to transmit sound waves from eardrum to inner ear
Hyoid bone
Serves as the base for the tongue from above is attached to the larynx below and the pharynx posteriorly and is located in upper neck and is an independent bone that does not contact any other bone
Appendicular skeleton (5):
- All bones of the upper and lower limbs and the bones that attach to each limb
- Limbs attach to the skeleton at girdles
- Upper limbs (arms) attach to a shoulder girdle
- Lower limbs (legs) attach to pelvic girdle
- Functions to move the body and interact with environment
Bones of appendicular skeleton region (6)
- 126 bones total in adult
- Bones are divided into the bones of the limbs themselves and those of the girdles to which they attach
- 30 bones in upper limbs
- 30 bones in lower limbs
- 4 bones in pectoral girdle
- 2 bones in pelvic girdle
Function of bones of lower limbs
Adapted for weight bearing support and stability and body locomotion
Function of bones of upper limbs
Highly mobile and can be utilized for a wide variety of functions
Vertebral column
Known as spinal column/spine consisting of bones called vertebrae each separated by intervertebral disc
Vertebral column function
Flexible so it supports the head, neck, body, and allows for their movements. It also protects spinal cord which passes down the back through openings in vertebrae
Vertebrae in vertebral column (6):
- Develops as 33 vertebrae but reduced to 26
- 7 cervical vertebrae
- 12 thoracic vertebrae
- 5 lumbar vertebrae
- Single sacrum also part of pelvis formed by fusion of 5 sacral vertebrae
- Single coccyx (tail bone) formed by fusion of 4 small coccygeal vertebrae
The 4 curvatures of the vertebral column
Adult vertebral column has four curvatures along its length that increase strength, flexibility and ability to absorb shock; cervical, thoracic, lumbar, pelvic
Vertebral column in fetal development
Flexed anteriorly into fetal position, giving the entire vertebral column a single curvature that is concave anteriorly
Parts of a vertebra (3)
- Body
- Vertebral arch
- Seven processes
Body
Anterior portion and is the part that supports body weight
Vertebral arch
Forms posterior portion of each vertebra
Vertebral foramen
Large opening between vertebral arch and body that contains the spinal cord
Vertebral canal
Bony protection and passageway for spinal cord down the back where all the vertebral foramina of the vertebrae align
Intervertebral foramen
Opening between adjacent vertebrae formed by notches in pedicles and allows spinal nerves to exit the vertebral column
Where do the 7 processes arise
From the vertebral arch
Transverse process (3)
- Paired structures
- Project laterally from vertebrae
- Serves as sites for muscle attachment
Spinous process (3)
- Single structure
- Projects posteriorly at midline of back
- Serves as site for muscle attachment
Articular process (3)
- Superior and inferior processes
- Allows for slightly movable joints between adjacent vertebrae
- Superior process extends upward, white inferior process extends downward
Intervertebral disc
Made of fibrocartilage that separate the bodies of adjacent vertebrae
Cervical vertebrae
Body is small, carrying less weight, has Bifid (Y-shaped) spinous process, transverse process (U-shaped) with opening called transverse foramen
C1 (atlas) function and structure (4):
- Supports skull
- No body or spinous process
- Ring shaped; anterior arch and posterior arch
- Transverse processes of atlas are longer and extend more naturally than other cervical vertebrae
Superior articular processes
Face upward and are deeply curved for articulation with occipital condyles on base of skull
Inferior articular processes
Flat and face downwards to join with superior articular processes of C2 vertebra
C2 (axis) functions and structures (4)
- Serves as axis for rotation when turning the head towards right or left
- Resembles a typical cervical vertebrae
- Contains dens (bony projection that extends upward from vertebral body)
- Dens join with inner aspect of anterior arch of atlas where it is held in place by transverse ligament
Thoracic cage
AKA ribcage and forms the thorax (chest) portion of body to protect heart and lungs. It contains 12 pairs of ribs with costal cartilages (made of hyaline cartilage) and sternum. The ribs are anchored posteriorly to 12 thoracic vertebrae (T1-T12)
Sternum
Elongated body structure that anchors anterior thoracic cage consisting of 3 parts; manubrium, body, xiphoid process
How are ribs classified
Classified into 3 groups based on relationship to the sternum
Ribs 1-7
True ribs; coastal cartilage attaches directly to sternum
Ribs 8-10
False ribs; coastal cartilage do not attach directly to sternum and instead attach to the cartilage of the next rib
Ribs 11-12
Floating ribs; do not attach to sternum at all
Ribs 11-12
Pectoral girdle
Bones that attach each upper limb to axial skeleton
Clavicle
AKA collarbone is an S shaped bone located anterior side of shoulder and attached on its medial end to sternum of thoracic cage part of axial skeleton
Scapula
AKA shoulder blade is flat and triangular shaped that lies on posterior aspect of shoulder and supported by clavicle and articulates with humerus (upper arm bone) to form shoulder joint
3 regions of the upper limb (4)
- Possesses 30 bones
- Arm
- Forearm
- Hand
Arm
Single bone called humerus between shoulder and elbow joints
Forearm
Bones called ulna and radius found in forearm located between elbow and wrist
Hand
Base of hand contains 8 carpal bones while the palm of hand has 5 metacarpal bones, and the digits (fingers and thumbs) contains 14 phalanx bones
Head on humerus proximally and distally
Located on proximal end of humerus and is a large, round, smooth region that face medially. Distally, the humerus becomes flattened and has 2 articulation areas which join ulna and radius bones of forearm to form elbow joint
Shoulder joint
When the head articulates with the scapula
Radius
Runs parallel to ulna on lateral side of forearm
Head of radius proximally and distally
Proximal head is disc shaped while distal end has a smooth surface for articulation with two carpal bones to form wrist joint
Ulna
Medial bone of forearm and runs parallel to radius
Carpal bones
Series of 8 small bones that form the wrist and base of hand arranged in two rows of four
Palm structure
Contains 5 metacarpal bones that lie between carpal bones and phalanx bones of fingers and thumb
Thumb structure
Has 2 phalanges
Finger 2-5 structure
Has 3 phalanges each
Pelvic girdle structure and function
Formed by a single hip bone (coxal bone), one on each side of body. Bones of pelvis are strongly united to each other to form a largely immobile weight bearing structure. It also serves as an attachment point of lower limb
Pelvis
Entire structure formed by two hip bones, sacrum, and attached inferiorly to sacrum and coccyx
Pectoral girdle
Highly mobile and enhance range of upper limb movements
Hip bone structure
Large, curved bones that form lateral and anterior aspects of pelvis. Each adult hip bone is formed by e separate bones that fuse together during late teenage years
Components/regions of hip bone (3):
- Ilium
- Ischium
- Pubis
Ilium
Fan-like superior region that forms the largest part of the hip bone. It is firmly united to the sacrum at the largely immobile sacroiliac joint
Ischium
Forms the posteroinferior region of each hip bone
Pubis
Forms the anterior portion of hip bone and curves medially where it joins the pubis of the opposite hip bone at a specialized joint called pubic symphysis
Female pelvis characteristics (5):
- Pelvic weight; Lighter and thinner bones
- Pelvic inlet shape; Round/oval
- Lesser pelvic cavity shape; Shorter and wider
- Subpubic angle; Greater than 80 degrees
- Pelvic outlet; rounder and larger
Male pelvis characteristics (5):
- Pelvic weight; thicker and heavier bones
- Pelvic inlet shape; Heart shaped
- Lesser pelvic cavity shape; Longer and narrower
- Subpubic angle; Less than 70 degrees
- Pelvic outlet shape; Smaller
3 regions of lower limb (4):
- Contains 30 bones
- Thigh
- Leg
- Foot
Femur
Single bone in thigh (portion of leg from hip joint to knee joint) and is the longest and strongest bone of body
Patella
Kneecap and articulates with distal femur
Tibia
Medial bone of leg and main weight bearing bone of lower leg and second longest bone of body (region from the knee join to ankle joint)
Fibula
Slender bone located on lateral side of leg and does not bear weight as it serves primarily for muscle attachments
3 bones of the foot
Tarsal bone, metatarsal bone, phalanx bone
Tarsal bone
Posterior half of foot formed by 7 tarsal bones
Talus
Most superior tarsal bone that articulates with tibia and fibula to form ankle joint
Calcaneus
Largest bone of foot which forms the heel
Metatarsal bone
Anterior half of foot formed by 5 metatarsal bone
Phalanx bone
14 of these present in toes arranged similarly to finger
Big toe
Has 2 phalanx bones
Remaining toes
Has 3 phalanx bones each
