Bones

Long Bones

are longer than they are wide

Short bones

have almost the same length as width

Flat bones

are broad and flat

Irregular bones

have many projection for articulation

Sesamoid bones

are wrapped in a tendon

Sutural bones

are small, flat bones that are found near a suture

Diaphysis

central shaft of the long bone

Epiphyses

are the knobs at the ends of the diaphysis ( proximal & distal)

Articular Cartilage

protective cartilage that the two epiphyses

Metaphysis

is the region between diaphysis and epiphysis with the epiphyseal line that represents the remnant of the epiphyseal plate

Medullary cavity

is a cavity in diaphysis, filled with fatty yellow bone marrow, blood vessel and nerves

Periosteum

covers the outer surface of the diaphysis

Endosteum

thin membrane that covers the inner surface of the medullary cavity

Bone markings

sites on the bones that provide sites for articulation, attachment of ligaments and tendons, forms passages and cavities for blood vessels and nerves

Foramen

hole in a bone as a passageway for blood vessels and nerves

Fissure

opening between the bones for nerves to pass

Meatus

canal-like opening in a bone

Sinus

hollow space within a bone

Fossa

depression in a bone for muscle attachment or for one bone fits into another

Alveolus

socket in which the teeth fit into the jaws

Sulcus

groove on bone surface for a tendon, a blood vessel or nerve to be protected

Head

large, rounded projection for articulation on long bones

Facet

smooth, flat surface where another bone articulates

Condyle

smooth rounded surface for articulation

Epicondyle

projection superior to a condyle that is a site for muscle attachment

Process

any bony projection

Trochanter

large processes which serve as sites for muscle attachment

Tubercle

small rounded process

Tuberosity

rough surface for muscle attachment

Functions of the skeletal system

• provides support

• protect the internal organs

• assists body movements

• Mineral homeostasis - stores and releases calcium and phosphorus

• participates in blood cell production (hemopoiesis)

• stores triglycerides in adipose cells of yellow marrow

What does the long bone consist of?

• diaphysis

• 2 epiphyses

• 2 metaphyses

• articular cartilage covering both epiphyses

• Periosteum(connective tissue)

• medullary cavity

• endosteum

What are the long bones & what do they do?

• radius, ulna, femur, humerus, Tibia, Fibula

• makes blood

What is the epiphysis is made of?

Spongy bone( contains red bone marrow which makes blood cells)

What is the diaphysis made of?

Compact bone

What is the function of articular cartilage?

cushion between bones

What is the function of the epiphyseal line?

has consistent supply of cartilage building cells

What is the medullary cavity made of and what does it do?

• made up of yellow marrow

• produces blood and stores fat

What is the endosteum made of?

clusters of bone cells/osteoprogenitor cells

What is bone extracellular matrix made of?

15% water, 30% collagen, 55% crystalized mineral salts

What are the 4 types of bone cells and what are their functions?

• Osteoprogenitor cells - bone stem cells able to differentiate into the other types of cells

• Osteoblasts - bone-building cells that secrete matrix

• Osteocytes- mature bone cells

• Osteoclasts- remodel bones and cause them to release calcium

What does compact bone provide?

provides protection and support

What does spongy bone provide?

It’s lightweight and provides tissue support

What are periosteal arteries?

enter the diaphysis through Volkmann’s canals and are accompanied by periosteal veins and are accompanied by periosteal veins

What is a nutrient artery?

enters the center of the diaphysis through a nutrient foramen. Nutrient veins exit via the same canal

What is ossification(osteogenesis) and what 4 situations does it form in?

• the process of bone formation

• forms during embryological and fetal development, when bones grow before adulthood, when bones remodel, when factures heal

What bones does intramembranous ossification occur in?

flat, irregular, sesamoid, sutural

What are the steps of intramembranous ossification?

1. Development of ossification center: osteoblasts secrete organic extracellular matrix

2. Calcification: calcium and other mineral salts are deposited and extracellular matrix calcifies

3. formation of trabeculae: extracellular matrix develops into trabeculae that fuse to form spongy bone

4. Development of the periosteum: mesenchyme at the periphery of the bone develops into the periosteum

Where do bones come from?

They come from cartilage.

What is endochondral ossification?

replaces cartilage with bone in the developing embryo and fetus and occurs in epiphyseal plates of long bones as they grow in length

What are the steps of endochondral ossification?

1. Development of cartilage model: Mesenchymal cells develop into chondroblasts which form the cartilage model.

2. Growth of cartilage model: growth occurs by cell division of chondrocytes

3. Development of primary ossification center: In this region of the diaphysis, bone tissue has replaced most of the cartilage

4. Development of the medullary (marrow) cavity. Bone breakdown by osteoclasts forms the medullary cavity

5. Development of secondary ossification centers: These occur in the epiphyses of the bone

6. Formation of articular cartilage and epiphyseal plate: Both structures consist of hyaline cartilage

How do bones thicken?

cooperative action of osteoblasts and osteoclasts

-osteoblasts deposit bone on the outer surface

• osteoclasts widen the medullary cavity from within

What are the steps of the healing process of bones?

1. reactive phase- early inflammation phase & formation of a fracture hematoma

2. reparative phase- includes formation of a fibrocartilaginous callus first and a bony callus second

3. bone remodeling phase- last step as the bony callus is remodeled by osteoclasts

What are the different types of fractures?

open, closed, comminuted, greenstick, impacted, pott, colles

What is an open/compound fracture?

the broken ends of the bone protrude through the skin

What is a closed/simple fracture?

does not break the skin; bone just breaks

What is a comminuted fracture?

The bone is splintered, crushed or broken into pieces at the site of impact, and smaller bone fragments lie between the two main fragments

What are greenstick fractures?

(usually in ulna & radius) a partial fracture in which one side of the bone is broken and the other side bends; similar to the way a green twig breaks on one side while the other side stays whole, but bends; occurs only in children, whose bones are not fully ossified and contain more organic material than inorganic material

What is an impacted fracture?

One end of the fractured bone is forcefully driven into the interior of the other (seen in skate borders & car accident victims without seatbelts)

How much of the body’s calcium do the bones hold?

99%

What is the role of the parathyroid gland in calcium homeostasis?

• secretes parathyroid hormone when calcium levels drop

• osteoclasts are stimulated to increase bone resorption and calcium is released

What else does parathyroid hormone stimulate?

stimulates the production of calcitriol(active form of vitamin D) by the kidneys to increase calcium absorption in the intestines & tells kidneys to not excrete Ca in the urine

What is the function of calcitonin?

released to lower blood Ca levels by the thyroid gland, osteoblast activity increases

What happens with bone tissue as we age?

decrease in bone mass when resorption outpaces deposition

What is the function of growth hormone?

secreted by the anterior lobe of the pituitary gland; promotes general growth of all body tissues , including bone, mainly by stimulating production of insulin- like growth factors

What is the function of the thyroid hormones (T3 & T4)?

secreted by the thyroid gland; promotes normal bone growth by stimulating osteoblasts

What is the function of insulin?

secreted by the pancreas; promotes normal bone growth by increasing the synthesis of bone proteins

Sex hormones (estrogens and testosterone)

stimulate osteoblasts and promote the sudden growth spurt that occurs during adolescence; shut down growth at epiphyseal plates around 18-21, causing lengthwise growth of bone to end; contributes to bone remodeling during adulthood by slowing bone resorption by osteoclasts and promoting bone deposition by osteoclasts

What is the effect of exercise on the bone?

weight-bearing activities stimulate osteoblasts and help build thicker, stronger bones

prevents loss of bone mass as people age

How many bones are in the axial skeleton and what bones consist of it?

• 80 bones

• skull bones, auditory bones, ossicles, hyoid bone, ribs, sternum, vertebrae and sacrum

How many bones are in the appendicular skeleton and what bones consist of it?

• 126 bones

• bones of the upper and lower extremities, bones forming girdles that connect limbs to the axial skeleton

What is a crest marking?

prominent ridge or elongated projection

What is a line marking?

long, narrow ridge or border(less prominent that crest)

What is a spinous process?

sharp, slender projection

What is a fontanel?

areas of a fetus/baby where unossified mesenchyme develops into dense connective tissue

What is the function of the hyoid bone?

• does not articulate with any other bone

• supports the tongue and provides an attachment site for some muscles of the neck and pharynx

What is the function and structure of the vertebral column?

• protects the spinal cord

• composed of 26 vertebrae dived into 5 regions( cervical: 7, thoracic: 12, lumbar: 5, sacrum, coccyx)

What are the curves of the spinal cord?

cervical, thoracic, lumbar, sacral

What is the structure and function of the intervertebral discs?

• located between the bodies of the vertebrae from the second cervical to the sacrum

• composed of an outer ring of fibrocartilage(annulus fibrosus) and an inner, soft nucleus(nucleus pulposus) with a layer of hyaline cartilage on the top and bottom of each disc

• absorb shock and separate the vertebrae from one another

What is the specific name of the C1 vertebrae?

atlas

What is the specific name of the C2 vertebrae?

axis

What is the function of the thoracic vertebrae?

support the ribs and have special structures for rib head and tubercle attachment

What is the function of the lumbar vertebrae?

• largest and strongest vertebrae

• no special structures that are specifically associated with these vertebrae

What is the structure of the sacrum?

• triangular shaped

• part of the pelvic girdle

• composed of 5 vertebrae that fuse

What is the structure of the coccyx?

• much smaller than the sacrum

• triangular in shape

• composed of 4 vertebrae that fuse

What is the thorax and what is it composed of?

• entire chest region

• composed of the sternum, ribs, and costa cartilages (make up thoracic cage)

What are the 3 segments of the sternum?

upper manubrium, middle body, lower xiphoid process

What is the function of the sternum?

articulates with the clavicles and the costal cartilages

How many pairs of ribs are there?

12 pairs of ribs

What is the function of the ribs?

provide structural support to the thoracic cavity

What are the categories of the ribs?

• True(vertebrosternal) ribs- first 7 pairs; their cartilage is directly connected to the sternum

• False(vertebrochondral) ribs- next 5 pairs; cartilage is indirectly connected to the sternum

• Floating(vertebral) ribs- last 2 pairs; these are not connected to the sternum

What are the curve-related disorders of the spine?

• Scoliosis(increased lateral curvature)

• Kyphosis(increased thoracic curve-bent forward)

• Lordosis(increased lumbar curve- bent backwards)

What is spina bifida?

a congenital defect of the vertebral column where the laminae do not develop normally (vary from minor to severe)

Where do fractures of the vertebral column most frequently occur?

at C1, C2, C4-T, and T12-L2 (can cause spinal cord or nerve damage)

What makes up the pectoral (shoulder) girdle?

clavicle and scapula

What are the articulations for the clavicle?

• medial(sternal) end articulates with the manubrium of the sternum

• lateral (acromial) end articulates with the acromion of the scapula

What is the scapula and what does it articulate with?

• flat bone that is located in the superior part of the posterior thorax between the second and seventh ribs

• glenoid cavity attaches to the humerus

What does the humerus articulate with?

• head of humerus articulates with the glenoid cavity of the scapula

• trochlea articulates with the ulna and the capitulum with the radius

What does the ulna articulate with?

• the olecranon and coronoid process at the proximal end of the ulna form the trochlear notch which wraps around the trochlea of the humerus making the elbow joint

• head of radius with the capitulum of the humerus and with the ulna allow the forearm to rotate

What do the carpal bones articulate with?

(8 small bones)

scaphoid, lunate, triquetrum, pisiform - articulates with the distal radius

trapezium, trapezoid, capitate, hamate- articulates with the metacarpals