What is the function of the skeletal system?
Structure, support, protection, locomotion, it is a site for blood formation, storehouse for inorganic minerals (Ca!), and it is an indicator of sex, height, weight, racial background, and medical history
What are the types of bones when classified by shape?
Long bones, short bones, flat bones, irregular bones, pneumatic bones, and sesamoid bones
What are long bones?
They are bones that are longer than wide, cylindrical with a medullary cavity, and are the main components of limbs
What are short bones?
They are roughly cubical (carpals and tarsals) and are found where mobility is needed, but space is limited
What are flat bones?
Relatively thin bones that provide a broad surface for muscle attachment and/ or protection of underlying organs
What are irregular bones?
They are bones with an irregular shape and numerous projections (vertebrae)
What are pneumatic bones?
They contain sizable air spaces; only found in some bones of the skull. They help to reduce the weight of the skull
What are sesamoid bones?
They are small round bones embedded within a tendon. They alter the angle of muscle attachment to increase leverage
What are accessory bones?
Abnormal bone growth from an existing normal bone (bone spurs)
What are heterotopic bones?
Abnormal bone, formed entirely within soft tissue (kidney and gall stones)
What composes the axial skeleton?
Bones of the skull, hyoid, vertebral column, and rib cage
What composes the appendicular skeleton?
Bones of the limbs and their attachment onto the axial skeleton
What composes the cranial skeleton?
Bones of the skull
What composes the post-cranial skeleton?
Bones of the vertebral column, hyoid, rib cage, limbs, pectoral girdle, and pelvic girdle
What is the diaphysis?
The bone shaft and the primary center for ossification
What is the epiphysis?
Secondary site of ossification and is generally associated with the area of articulation with another bone
What is the epiphyseal plate?
It is a disk of hyaline cartilage that separates the diaphysis and epiphysis
What is the periosteum?
A layer of dense irregular connective tissue covering outer bone surface.
What anchors the periosteum to the outer surface of the bone?
Sharpey’s fibers
What are the two layers of periosteum?
Outer fibrous layer, which contains type I collagen and fibroblasts, blood vessels, and nerve fibers.
Inner cellular layer, which contains bone cells (osteoprogenitor and osteoblasts)
What is the endosteum?
A very thin connective tissue layer covering inner bone surfaces
Primarily consists of a single layer of osteoprogenitor cells and osteoblasts
What is the medullary cavity?
Cavity at the center of a long bone
What is articular cartilage?
A covering of articular surfaces; composed of hyaline cartilage
What two components is bone tissue made of?
Fibers and ground substance
What fibers primarily compose bone tissue?
Type I collagen, but does have some type V
What does collagen do for the bone?
It provides the strength to resist tensile forces
What two components is the ground substance of bones made of?
An organic component (proteoglycans: chondroitin sulfate, keretan sulfate, and hyaluronic acid and glycoproteins: osteonectin and osteocalcin)
An inorganic component (hydorxyapatite:calcium carbonate and calcium phosphate)
What does hydroxyapatite do for the bone?
Ir provides the strength to resist compressive forces
What are osteoprogenitor cells
They are cells located in the cellular layer of the periosteum and in the endosteum. They give rise to osteoblasts
What are ostseoblast?
They give rise to new bone tissue and are located within the central and perforating canals within the periosteum and endosteum
What are osteocytes?
Former osteoblasts that maintain surrounding bone tissue and regulate mineral content. They are located in the lacunae
What are osteoclasts?
Bone destroying cells. They are large and multinucleated, originating from the fusion of several monocytes
What are the two types of bone tissue?
Primary (woven) and Secondary (mature/lamellar) bone
What is primary (woven) bone tissue?
It develops first during fetal development and collagen fibers are randomly arranged. Mineral content is lower and it contains more osteocytes than mature bone tissue
What is secondary (mature/lamellar) bone tissue?
Compact bone, spongy bone, and subchondral bone
What are osteons?
They are a system within bone tissue that is composed of lamellae, central canals, lacunae, canaliculi, and perforating canals
What is lamellae?
Concentric layers of bony connective tissue; within each layer, the collagen fibers are orientated at right angles to the fibers in adjacent layers
What are central canals?
Contains vascular structures and nerves
What are lacunae?
Holes found between lamellae
What are canaliculi?
Passageways connecting lacunae to each other and to the central canal
What are perforating canals?
Canals connecting central canals to each other
What is circumferential lamellae? What types are there?
Multiple layers of mineralized matrix. There is external circumferential lamella and inner circumferential lamella
What is external circumferential lamella?
It is lamella that is located immedicately deep to the periosteum
What is internal circumferential lamella?
It is lamella that is located at the perimeter of the medullary cavity
What is interstitial lamella?
Layers of mineralized matrix, lying between and around osteons. The remains of partially destroyed osteons
What is spongy bone?
It is a lattice/network of bony bars and struts (trabeculae) each consisting of a few concentric layers of bony connective tissue. It is found in the interior of a bone
What is subchondral bone?
A very thin layer of modified compact bone, lacking extensive vascular channels. It is found underlying articular cartilage
What is Wolff’s Law?
A bone remodels its shape according to the way force is transmitted through it
What types of developmental bone is there?
Intramembranous (bones at the top of the skull and clavicle) and endochondrous (bones of the skull base and all postcranial bones, including parts of the clavicle
What is the process of endochondral bone formation?
Cartilaginous model forms, cartilage disintegrates and excavates the interior of the bone, blood vessels invade the cavity bringing mesenchymal cells, which differentiate into osteoblasts and start forming spongy bone. Periosteum then forms with the osteoblasts beneath forming compact bone. Further growth occurs in two directions: between the diaphysis and epiphysis (interstitial growth) and an increase in overall size (appositional growth)
What is interstital growth?
It is characterized by an epiphysial plate, which is the site of active growth between the epiphysis and diaphysis. Growth stops when the plate ossifies
What is appositional growth?
It is an increase in overall size of the bone. New bone is deposited by osteoblasts just below the periosteum. Osteoclasts at the inner bone surface enlarge the medullary cavity and remodel compact bone/spongy bone interface
What is the process of intramembranous bone formation?
Membranes form around blood vessels, undifferentiated connective tissue cells around blood vessels differentiate into osteoblasts that form spongy bone. The periosteum forms with osteoblasts forming compact bone beneath. The remaining growth takes place via a mechanism similar to appositional growth of endochondral bone
Where does bone deposition take place?
On the diaphyseal side of the epiphyseal plate
This vitamin is necessary for proper collagen formation and a deficiency leads to scurvy.
Vitamin C
This vitamin is synthesized within the skin or ingested as part of the diet. It facilitates proper bone mineralization by increasing absorption of calcium within the small intestine and reabsorption of calcium in the kidneys.
Vitamin D
A deficiency in vitamin D leads to what in children and what in adults?
Rickets (bones getting soft; bowing) in children and osteomalacia (chronic fatigue and joint pain) in adults
This hormone increases the amount of calcium in the blood by stimulating osteoclast activity. Also decreases the amount of phosphate in the blood
Parathyroid hormone (PTH)
How does PTH increase the amount of calcium in the blood?
It binds to receptors on the osteoblasts, which release osteoprotegerin ligand (OPGL), which activates receptors on preosteoclasts, which causes them to mature and then start breaking down bone tissue
What does an excess in PTH lead to?
Bone thinning
An excess in this hormone leads to gigantism in children and acromegaly in adults.
Pituitary growth hormone (GH)
What is a greenstick fracture?
It is an incomplete fracture, and the break occurs on the convex surface of the bend in the bone. Typically occurs in children
What is a compression fracture?
Some kind of compressive force acting on the bone to the extent of fracture. Can occur in long bones
What is a comminuted fracture?
It is a complete fracture and fragments the bone
What is the process of healing a fracture?
Fracture hematoma is formed from the ruptured blood vessels, soft callus forms (mixture of spongy bones and fibrocartilage), hard callus forms by mineralization of the soft callus, and remodeling of the hard callus to mature bone
What is osteitis?
An inflammation of bone tissue caused by injury or infection
What is periosteitis?
Inflammation of periosteum caused by trauma or infection
What is osteomyelitis?
Inflammation of bone interior caused by bacteria
What is tuberculosis in terms of bone tissue?
It is a bacterial infection than can spread to the spongy bone (particulary of the vertebral bodies), resulting in bone and joint destruction
During aging there is an ____ in osteoclast activity and ____ decrease in osteoblast activity.
Increase, Decrease
Women lose bone mass ____ and _____ than men.
Sooner and faster
What is osteoporosis?
It is a reduction in bone mass and is most prevalent in middle-aged and elderly women
What type of joint is immovable?
Synarthosis
What type of joint is slightly moveable?
Amphiarthrosis
What type of joint is freely moveable?
Diarthrosis
What types of fibrous joints are there?
Syndesmosis, suture, and gomphosis
What is a syndesmosis?
Bones joined by a fibrous band which forms an interosseous ligament. They are amphiarthrosis
What is a suture?
Bones joined by a very short fibrous band, which forms a sutural ligament. They are synarthrosis
What is a gomphosis?
They are the articulations between tooth roots and bony socket. Consists of a very short fibrous band which forms a periodontal ligament and is classified as synarthrosis
What types of cartilaginous joints are there?
Synchondrosis and symphsis
What is a synchondrosis?
Bones that are united by a plate of hyaline cartilage. They are synarthrosis
What is a symphysis?
Articular surfaces are covered by a thin layer of hyaline cartilage, which in turn is attached to a pad of fibrocartilage. They are amphiarthrosis
What is a synovial joint?
It is a space between articulating bones that is filled with synovial fluid. It is classified as a diarthrosis
What are the two components of a synovial joint?
Articular cartilage and a joint capsule surrounding the joint
What are the components of the joint cavity of a synovial joint?
A fibrous layer (capsular ligament) and a synovial membrane (covers all non-cartilaginous surfaces)
What are the two layers of the synovial membrane?
A deep fibrous layer composed of collagen fibers and fibroblasts and a superficial cellular layer composed of synoviocytes, blood vessels, and collagen fibers
What are the two types of synoviocytes?
Macrophage-like and fibroblast like cells
What is the function of the macrophage-like synoviocytes?
They are in direct contact with the synovial fluid and phagocytize any debris that may be floating the fluid
What is the function of the fibroblast-like synoviocytes?
They are farther away from the synovial fluid and produce hyaluronic acid which is a component of the fluid
What are the two components of synovial fluid?
Hyaluronic acid and blood plasma
What is the function of synovial fluid?
It acts as a lubricant, cushion, and nourishes articular cartilage
What is the articular disk/meniscus?
It is fibrocartilage pad located between articular surfaces and acts as a shock absorber, limiter of motion within the joint, and it stabilizes the joint
What is a bursa?
It is a closed synovial fluid-filled sac
What is a ball and socket joint (spheroidal)?
The globular surface of one bone articulates with a cup-shaped surface of another bone. It is multiaxial
What is a condyloid (ellipsoidal) joint?
The convex oval shaped surface of one bone articulates with a concave elliptical surface of another bone. It is biaxial
What is a saddle (sellar) joint?
The articulating surfaces have both concave and convex regions; surface of one bone fits the complementary surface of another. It is biaxial
What is a gliding (arthrodial) joint?
Articulating surfaces are nearly flat. It is nonaxial
What is a hinge (ginglymoidal) joint?
The convex cylindrical surface of one bone articulates with concave cylindrical surface of another. It is uniaxial
What is a pivot (trochoidal) joint?
The cylindrical pin of one bone rotates within a ring formed of bone and ligament. It is uniaxial
What is angular movement?
Movements within a sagittal or coronal plane of the body
What are some examples of angular movements?
Sagittal plane: Flexion, extension, hyperextension, dorsiflexion, and plantar flexion (at the talo-crunal/ankle joint)
Coronal Plane: Abduction, and adduction
What is circular movement?
Rotation: movement of a body part around its own long axis
Circumduction: Movement in which the distal end of the segment moves in a circle while the proximal end remains fixed
What are some examples of circular movement?
Supination and pronation at the proximal radioulnar joint
What is inversion and eversion?
Movements of the sole of the foot medially or laterally, respectively
What is elevation and depression?
Movement of a body part upwards or downwards, respectively
What is protraction and retraction?
Movement of a body part forward or backward, respectively, parallel to the horizontal surface
Give an example of these joints: ball and socket, condyloid, saddle, gliding, hinge, and pivot.
Ball and socket: shoulder and hip joints Condyloid: MP joint of the hand Saddle: the joint of the CP joint of digit 1 Gliding: the carpals of the hand Hinge: elbow joint Pivot: atlas and axis
What is a dislocation?
A displacement of a bone within a joint; partial (subluxation) or total (luxation)
What is a sprain and how is it difficult from a strain?
A sprain is an overstretching or tearing of ligamentous tissue whereas as a strain is an overstretching of muscle
What is bursitis?
An inflammation of a bursa
An autoimmune disease involving synovial joints. It is characterized by inflammation of the synovial membrane, resulting in the production of abnormal secetions
Rheumatoid arthritis
What are the two types of secretions in rheumatoid arthritis?
Granular secretions: destruction of the articular cartilage
Fibrous secretions: they fill up the joint cavity to the point that the joint can ossify and fuse together
It is a progressive degeneration of the synovial joints through wear and tear.
Osteoarthritis
What is osteoarthritis typically associated with?
The development of accessory bone at the periphery of joint surfaces and degradation of articular cartilage
What types of joints are typically affected by osteoarthritis?
High use joints, traumatized joints, and large weight bearing joints