UARK Anatomy Exam 2 - Becker

Skeletal system

Axial

Appendicular

Cartilage

Ligaments

axial

skull, spine, thoracic cavity

Appendicular

limbs, pectoral girdle, pelvic girdle

Support

framework for attachment of other organs

Movement / locomotion

muscles use bones as levers

Storage of minerals

Calcium ions

phosphate ions

Blood cell production (hematopoiesis)

bone marrow produces erythrocytes, leukocytes, & platelets

protection

Ribs protect heart & lungs

Skull protects brain

Vertebrae protect spinal cord

Pelvic bones protect reproductive organs

Matrix of bone consists of

Hydroxyapatite crystals: mainly calcium phosphate (and calcium hydroxide) will resist compression, but inflexible

Calcium phosphate makes up ~2/3 of bone mass

Collagen fibers

Make up ~1/3 of bone mass

Contribute to tensile strength of bones

Imparts limited flexibility to matrix

Bone cells

Contribute only ~2 percent of bone mass

Osteocytes

maintains matrix

Osteoblasts

produces matrix

Osteoprogenitor cells

produce osteoblasts

Osteoclasts

break down matrix

Osteoprogenitor cells: bone stem cells

Innermost layer of periosteum & inner lining of endosteum

Differentiate to form new osteoblasts

Involved in repair of bones after a fracture

Osteoclasts: multinucleated cells

osteolysis: secrete HCL, dissolving bones causing release Ca2+ & PO4 3- into blood

Osteoblasts: Immature bone cells

Found on inner & outer surfaces of bones

Produce osteoid: organic mix dumped into matrix

Osteogenesis: new bone formation via calcification of osteoid leading to ossification

Osteocytes: Mature bone cells

Maintain protein & mineral content of matrix

Controls release & deposition of Ca2+ in/out of bone

Lacunae

depressions where osteocytes reside

lamella

osteocytes matrix

Canaliculi:

small channels from osteocytes to bone capillaries

Osseous tissue types

1. Compact bone (dense bone)

2. Spongy bone (trabecular bone)

Compact bone (dense bone)

- dense & solid

- Forms walls of bone

- Parallel compression

Spongy bone (trabecular bone)

- Open network of plates

Multidirectional or light strain

- Surrounds medullary cavity (open space)

bone marrow: connective tissue in medullary cavity

Epiphysis

ends of long bones

Diaphysis

shaft of long bones

Metaphysis

transition

Medullary cavity:

inner cavity of diaphysis

Epiphyseal line

"growth line"

gross anatomy of the humerus

the organization of compact and spongy bone

compact bone

A single osteon at higher magnification. The central canal appears black on this section

Spongy bone

- Arranged in parallel struts

- Trabeculae: branching plates

- Trabeculae form an open network

- Large trabeculae can have osteons

- Reduces weight of bones, but keeps strength

Functional Differences • Compact bone

Transmission of stress parallel to bone axis

- Osteon arrangement is parallel to bone axis

- Weak bone strength perpendicular to bone axis

Functional Differences Spongy bone

- Multidirectional or light strain

- Trabeculae are oriented along stress lines

- Has extensive cross-bracing

- Supports marrow

Yellow marrow

mainly adipose, energy store

- Medullary cavity

Red marrow

Production & storage of leukocytes, erythrocytes, & thrombocytes

- In epiphysis or spaces between trabeculae -not restricted to just long bones

Periosteum: Membrane on outer surface of bone

Fibrous layer & osteogenic layer (complete, multi cell layer)

• Isolates & protects bone from surrounding tissue

• Attachment for circulatory & nervous supply

• Actively participates in bone growth & repair

• Perforating fibers: anchors periosteum to bone & other connective tissues

• Attachment site for tendons & ligaments

Endosteum

membrane on inner surface of bone; single, incomplete cell layer

Lines medullary cavity, perforating canals & central canals

Both endosteum & periosteum have

- Osteoblasts: produces matrix

- Osteoprogenitor cells: produce osteoblasts

Appositional growth

Osteoblasts in periosteum add bone matrix to surface

• Forming circumferential lamellae on outer surface

• Osteons are formed

• Osteoclasts break down layer below endosteum to enlarge medullary cavity

- bone length typically set by age 25

Osteoblast & osteoclast activity is

equal in bones that aren't changing shape

Bones change shape in response to strain

Increased muscular development during exercise

- Inactivity of bones can cause degeneration

- After a few weeks, unstressed bones can lose ~1/3 mass; shape & density

Factors Regulating Bone Growth

Minerals: calcium, phosphate, magnesium, citrate, carbonate, sodium

Vitamins:

- A:

stimulates osteoblasts

-C:

collagen formation & osteoblast differentiation

- D3 :

used for calcitriol by kidneys

• Calcitriol: increase Ca2+ & PO4 3- absorption in small intestines

Hormones:

work to regulate plasma Ca2+ levels

Parathyroid hormone (PTH)

- Stimulates osteoclasts

• Increases circulating Ca2+

• Influences production of calcitriol in kidney

- Increase Ca2+ absorption from small intestines

Calcitonin (produced by thyroid gland)

Inhibits osteoclasts

- Decreases circulating Ca2+

• Removing Ca2+ from blood & deposit as bone

Thyroxine (thyroid gland) & Growth hormone (anterior pituitary gland)

- Influence basal metabolic rate of bone cells

-Maintain activity in epiphyseal region for growth

Estrogen & Testosterone

Stimulate osteoblast activity causing growth spurts during puberty

-Maintain bone density in adults

skeletal system

Houses central nervous system (CNS)

• Integration centers for reflex arcs

• Controls skeletal muscle

Houses senses

Sight • Hearing • Taste • Smell • Balance

CNS

Allows for sound production & communication

• Feeding

• Breathing

• Attachment points for appendicular system

Thoracic cage (thorax)

Ribs

• Sternum

• Thoracic vertebrae

• Costal cartilage

skull

Suture

dense fibrous connective tissue

Fontanelles

gaps between cranial sutures; gives flexibility to skull during parturition

lateral view of adult skull

inferior view mandible removed

Orbit made of

Frontal bone

• Maxilla bone

• Lacrimal bone

Ethmoid bone

• Sphenoid bone

• Zygomatic bone

sphenoid

ethmoid

right temporal bone

maxilla

palatine

mandible

sinuses

Produce mucus

• Resonate sound

• Lighten skull

• Humidifies air

section showing the positions of the paranasal sinuses

sagittal section with the nasal septum removed to show major features of the wall of the right nasal cavity

hyoid

Anchor point for muscles of:

• Tongue • Larynx

anterior and posterior views of the bones of the axial skeleton

vertebral regions

regions are defined by anatomical characteristics of individual vertebrae

views of vertebra

articulated vertebrae views

atlas & axis

spinous process of vertebra prominens

Sacrum

Anterior view of the rib cage and sternum

posterior and medial view showing major anatomical landmarks on an isolated right rib

axial skeleton

All of these examples are from right side of body

Sternoclavicular joint:

only direct connection between pectoral girdle & axial skeleton

Right clavicle, superior view

Right clavicle, inferior view

Scapula

Humerus

humerus posterior view

radius & ulna

Lateral view of the proximal end of the ulna

anterior view of the distal ends of the radius and ulna and the distal radio-ulnar joint

Anterior (palmar) view of the bones of the right wrist and hand