ANAPHY SKELETAL SYSTEM

Skeletal System

A living dynamic system made up of Bones, cartilage, and connective tissues that provides structure, support, and protection to the body while enabling movement.

Physiology of Skeletal System

Gives Shape
Maintains Stability
Ability to Move
Stem Cell Synthesis
Storage of Important Minerals like Calcium and Phosphate

Mesenchymal Stem Cells

Specialized stem cells in the embryonic mesoderm taht differentiate into the major-bone forming and bone-resorbing cells

Ostoprogenitor cell

MSC Origin, Precursor of Osteoblasts

Osteoblast

MSC Origin, Forms New Bone by producing Osteoid

Osteocyte

Osteoblast Origin, Maintain bone and senses Mechanical Stress

Osteoclast

Hematopoietic Stem Cell Origin, Break down/resorbs bone

Bone-lining Cell

Osteoblast lineage origin, covers inactive bone surfaces and helps regulate bone remodeling

Types of Bones

Long, Short, Flat, Irregular, Sesamoid, Pneumatic

Long Bones

Longer than they are wide, support body weight and facilitate movement

Examples of Long Bones

Femur, humerus, tibia, radius, ulna

Short Bones

Roughly cube-shaped, Probide stability and limited movement

Examples of Short Bones

Carpals of Wrist, Tarsals of ankles

Flat Bones

Thin, flattened, often slightly curved, protection and muscle attachment

Examples of flat bones

Skull bones, ribs, sternum, scapula

Irrecular bones

Complex shapes that don’t fit the other categories, protection support and muscle attachment

Examples of Irregular bones

Vertebrae, sacrum, facial bones

Sesamoid Bones

Small, round bones, embedded with TENDONS, protects tendons and improve mechanical advantage

Examples of Sesamoid bones

Patella

Pneumatic Bones

Contain air-filled spaces/SINUSES, Reduces skull weight and contribute to resonance

Examples of Pneumatic bones

Frontal, ethmoid, sphenoid, maxilla

Feature of Bones

important structural characteristics such as shape surface, projections depressions and openings. Allows bones to perform functions such as movement, rpotection, muscle attachment, and passage of nerves and blood vessels

Bone Projections

Are areas that STICK OUT from the bone, serving as attachment sites for muscles, tendons and ligaments

Types of Projections

Process, Tubercle, Tuberosity, Trochanter, Crest, Spine, Epicondyle, Condyle

Process

General Term for a Projection (IE MASTOID)

Tubercle

Small rounded projections (Greater ____ of Humerus)

Tuberosity

Large roughened projection (Tibial ____)

Trochanter

Very Large projection found ONLY ON the FEMUR (Greater ____)

Crest

Prominent Ridge (Iliac ____)

Spine

Sharp, slender projection (____ of Scapula)

Epicondyle

Projection located above a Condyle (Medial ____ of Humerus)

Condyle

Rounded, smooth projection FORMING a joint (Occipital _____)

Fossa

Shallow Depression (Olecranon ____)

Sulcus/Groove

Long, narrow depression (Intertubercular _____)

Notch

Indentation at the endge of a bone (Greated siatic ____)

Foramen

Hole or OPENING through a bone (_____ magnum)

Canal/Meatus

PASSAGE WAY through a bone (External Auditory ____)

Fissure

Narrow/slit light opening (superior Orbital _____)

Composition of Bone Tissue

Bone Cells+ Extracellular matrix

Extracellular Matrix of Bone

Organic Component (30%) and Inorganic Component (70%)

Organic Component (30%)

Provides Flexibility and Tensile Strength
Composed of: Type 1 Collagen Fibers + Ground Substance

Type 1 Collagen Fibers

Provide FLEXIBILITY and resistance to pulling forces

Ground Substance

Contains proteins and other substances that help organize and regulate the matrix

Inorganic Component (70%)

Provides HARDNESS and RESISTANCE to compression

Consits primarily of MINERAL SALTS like:

-Calcium Phosphate
-Hydroxyapatite crystals—magnesium and carbonate as well as calcium phosphate

Compact Bone

Dense, hard OUTER PORTION of bone

organized into structural units called OSTEONS (Haversian Systems)

Osteon (Haversian System) From superficial to deep

• Osteon → central canal → concentric lamellae → lacunae → canaliculi

Central Canal

Contains blood vessels and nerves in the bone

Lamellae

layers of the bone matrix

Lacunae

small spaces that CONTAIN osteocytes

Canaliculi

tiny chanells connecting osteocytes with each other and the blood suply

Spongy Bone/Cancellous or Trabecular bone

Consists of trabeculae—tiny bone plates

Trabeculae

Tiny bone plates in the spongy bone that contain bone marrow

Diaphysis

Long central shaft, Provides strength and support

Epiphysis

expanded ends of the bone, forms joins with other bones

Metaphysis

middle of diaphysis and epiphysis, contains the growthplate in the growing bones

Epiphysial plate

Cartilage growth plate in children/adolescents, allows bone to grow in length

Epiphysial Line

Remnant of the growth plate in adults, site where bone growth occured

Articular cartilage

Hyaline cartilage covering joint surfaces, Reduces friction and absorbs shock

Periosteum

Tough connective tissue covering the outer bone surface, protection nourishment repair and attachment of tendons and ligaments

contains

• Blood vessels 

• Nerves 

• Connective tissue 

• Bone-forming cells

Endosteum

Thin membrane lining internal bone surfaces, Contains cells involved in bone growth and remodeling

Lines the:
Medullary cavity 

• Internal surfaces of compact bone 

• Trabeculae of spongy bone

Medullary cavity

Hollow cavity inside the shaft, contains bone marrow

Compact bone

Dense outer later, provides strength and protection

Spongy bone

Porous bone found especially inside the epiphyses, Reduce weight and contain trabeculae

Harversian Canal

• microscopic tubes or tunnels in cortical bone that house nerve fibers and a few capillaries. 

• It allows bone to get oxygen and nutrition without being highly vascular. 

• It communicate with bone cells using special connections, or canaliculi.

Volkmann’s Canal

any of the small channels in bone that TRANSMIT BLOOD VESSELS FROM THE PERIOSTEUM INTO THE BONE, and that lie paerpendicular to and communicate with the harversian canals

Microscopic Structure of Bone from smallest to biggest (micro level)

osteocyte—lacuna—cancaliculi—lamella—central canal