Skeletal System Lecture Notes

Skeletal System Members

• The skeletal system is composed of:
  • Bones
  • Cartilage

Connective Tissues (Bones & Cartilage)

• Bones and cartilage are connective tissues.
• Sparse cell distribution in a matrix.
• The matrix consists of collagen proteins and proteoglycans.

Cartilage Types

• Hyaline cartilage: Provides smooth movement in joints.
• Elastic cartilage: More flexible and resistant to bending.
• Fibrocartilage: Most resistant; found in intervertebral discs.
• Cartilage contains chondrocytes (primary cells) derived from chondroblasts in the perichondrium.
• Cartilage is avascular, leading to slow repair.
• Chondroblasts are located in the perichondrium and secrete the cartilage matrix.

Bone Tissue

• Bone tissue, a connective tissue, consists of osteocytes in a hardened matrix.
• The matrix is hardened by minerals, primarily hydroxyapatite crystals (calcium and phosphate).
• Bones store and release calcium to maintain bodily calcium levels.

Bone Cells:

• Osteocytes: Primary bone cells.
• Osteoblasts: Secrete the bone matrix and eventually become osteocytes.
• Osteogenic cells: Stem cells that differentiate into osteoblasts.
• Osteoclasts: Macrophages that break down weakened or aged bone.
• Osteoblasts become trapped in lacunae (spaces) and extend processes to communicate with neighboring cells.

Bone Functions

• Provide body structure and support.
• Enable movement via muscle attachment.
• Bone marrow produces blood cells (hematopoiesis) using stem cells.
• Bones store minerals like calcium and phosphate.
• Yellow marrow stores fat.

Bone Classification

• Bones can be divided into the axial (head, vertebrae) and appendicular (limbs) skeleton.
• Bones are also classified by shape:
  • Long bones (e.g., femur, tibia)
  • Short bones (e.g., carpals, tarsals)
  • Flat bones (e.g., cranial bones, scapula)
  • Irregular bones (e.g., vertebra)
  • Sesamoid bones (e.g., patella)

Long Bone Structure:

• Diaphysis: The shaft or middle portion, composed of compact bone.
• Epiphysis: The ends of the bone, composed of spongy bone.
• Metaphysis: The segment between the epiphysis and diaphysis.
• Medullary cavity: Located within the diaphysis, it stores yellow bone marrow (fat).
• Spongy bone contains spaces filled with red marrow, responsible for blood cell production.
• The articular cartilage is present at the junction between bones.
• Periosteum: A protective layer of cartilage that wraps around the bone surface.
• Endosteum: A membrane lining the medullary cavity.
• Epiphyseal line: A remnant of the epiphyseal plate (growth plate).
• Nutrient artery: Supplies blood to the bone.

Bone Layers

• The outer layer of bone is the periosteum.
• The inner layer lining the medullary cavity is the endosteum.

Bone Tissue Types

• Compact bone forms the diaphysis and has a dense structure.
• Spongy bone is found in the epiphyses and metaphyses and has a sponge-like structure.

Compact Bone Structure

• Osteons: Microscopic structural units in compact bone.
  • Osteocytes: Bone cells that are located within lacunae.
  • Lacunae: Spaces that house osteocytes.
  • Central canal: Contains blood vessels and nerves.
  • Concentric lamellae: Concentric rings surrounding the central canal.
  • Perforating canals: Connect central canals between osteons, facilitating nutrient and waste transfer.

Spongy Bone Structure

• Trabeculae: Meshwork structure within spongy bone.
• Lacunae with osteocytes are present within trabeculae.
• Osteoclasts and osteoblasts remodel the bone surface.
• The space between trabeculae contains red bone marrow, where hematopoiesis occurs.

Bone Formation (Ossification)

• Bone formation begins with a cartilage model.
• The process of hardening is called ossification.
• Endochondral ossification: Cartilage is used as a template to become bone (long bones).
• Primary ossification center: Forms in the center of the long bone.
• Blood vessels bring osteoblasts to deposit minerals and harden the tissue.
• Chondrocytes continue to secrete cartilage at the ends, lengthening the bone.
• Secondary ossification centers: Develop at the epiphyses.
• Epiphyseal plate: Region where the primary and secondary ossification centers meet.

Bone Growth

• Longitudinal bone growth occurs at the epiphyseal plate.
• Chondrocytes proliferate, allowing the bone to lengthen.
• At adulthood, chondrocyte proliferation ceases, and bone replaces cartilage, forming the epiphyseal line.
• Appositional growth: Bone grows in width through the action of osteoclasts (chewing away aged bone) and osteoblasts (hardening the border).

Bones Need Blood

• Nutrient foramen: Openings that allow blood vessels to enter the bone.
• Bones are highly vascularized to nourish osteocytes.
• Sensory nerves present in bone transmit pain signals when the bone is injured.

Bone Repair After Damage (Fracture)

• Fracture: Damage/break to the bone.

Fracture Types:

• Closed: Fracture does not puncture the skin.
• Open: Fracture punctures the skin.
• Transverse, oblique, spiral, comminuted, impacted, greenstick
• Bone healing involves the formation of hematoma, followed by cartilage formation (callus).
• Callus: Cartilage formed to temporarily connect the bone.

Callus Types:

• Internal callus: Cartilage form inside the material cavity.
• External callus: Cartilage formed around the periosteum.
• The cartilage callus is eventually mineralized by osteoblasts (ossification).
• Weeks to months for bone to heal.
• Remodeling occurs with rehabilitation and physical therapy to adjust bone to physical demands.
• Exercise and vitamin D are necessary to slow bone density decline.
• Vitamin D:
  • Aide the absorption of Calcium from the small intestine, from absorption of calcium depends on vitamin D.
  • UV Light exposure:
    • The more UV light exposure you have the more it increases chances of skin cancer.
  • Vitamin D production:
    • UV help you protect you from the skin cancer, from the UV light induced skin damage, but it also pre reduce the production of vitamin D.
  • Vitamin D in Military:
    • Military personal build their health with strong bones and and a strong muscle.
  • Calcium in Kindey.
    • You won't increase them out and increase the calcium absorption by the. You will get the calcium from the bone and also from your urination.

Axial Skeleton Bones

• Bones Protect the central nervous system.

Bone Categories:

• Skull (cranial and facial bones)
• Vertebral column (cervical, thoracic, lumbar, sacral)
• Thoracic cage (ribs - 12 pairs)

Skull Bones:

• Cranial - protect the brain
• Facial - facial expression and provide structure.

Skull

• Cranial bones:
  • Frontal - forehead bones, (single bone)
  • Parietal - Top of head bone, (pair of bones)
  • Occipital - Back of head bone (single bone)
  • Temporal - Temple of head bone, (pair of bones)
• Sphenoid ethmoid - Inner part of forehead area. (single bone)
  • - bird or bat liking
• -A little strange structured.
• Facial bones:
  • Zygomatic - The upper area of the cheeks.
  • Nasal - Area of nose.
  • Maxilla - The bone of the front upper teeth.
  • Mandible- Bone of the bottom teeth.
• Suture ( Joint):
  • coronal; from frontal up to periatal.
  • squamous suture from here to there.
  • lumboid suture- The bone of the lower occipital area.

Superior view

• coronary that we just talked about.
• Sagittal - Has the zigzag area to the back bone.
• lumboid - the bottom occipital area
• Bregma- the junction between the frontal to sagittal suture.

Front view features ( Supraorbital Foramen):

• Orbital- the eye bone socket, contains the
• suprauptake foramen - above
• infraorbital foramen- Blow the eye bones.
• zygomatic arch of the temporal bone
  • zygomatic arch
• temporal process of the zygomatic bone
• Mental foramen- The area of the side of the mouth.
• Coronoid process - The top front inner ear part of the temporal bone area.
• lacrimal bones -The nose type bone of the orbital area to where the groove is at
• acoustic external .mutes - Sound tunnel of hearing.
• styloid process = the inner chin part.
• mastoid process- An outer bone area to where it connects the head bone.
• Two part to it tempora: upper or lower. The superier or the inferior.

Eye features

• optic canal - the eye visual nerves
• superior fissures- Eye ball movements
• inferior orbital fissures - Also eye movement support.
• Ethmoid - In the middle behind the nose under the brain for spinal support.
• Monto protuberous - Chin that has connected with muscle attachment.

Bottom view of bones ( palatine):

• palatine - small bone by to the top of your cavity.
• Vulmer - The long bottom bone center.
• Occipital condyle - The side hole of spinal attach.
• stytus process -The small bone
• mastoid. - The larger bone.
• Foramen magnum - Spinal connecting site. Has oxyptal protuberance feature.
• Jugular foramen - to allow the vein for nerves ( vagus). This would be a nerve that connected from Carotid.
• foramen ovule The hole of spinioid
  greater platine foramen In the top front back part .
• incisive fossa.
• Spinoid provides.

Ethmoid features

• optic canal It connects to vision.
• foramen ovum.
  • formamen lesserone.
  • - smaller hole.

Sphenoid features (The bottom half of head from back to forehead):

• lesser wing - Has long side area.
• greater wing- Has short side area.
• sera turkica.
• carotid canal This is that internal acoustic, - where music runs from. This is by the jugula.
• Hypoglossal this allows nerve with gland.

Mandible features ( lower part of bone the body):

• coronoid or condylar process - the two inner and outer line of bone.
• alveolar part.
• Mental - is where is has tunnel come from coming in and out.

the hyoid (Not attached with a bone):

• Digastric muscle where it have two gastric one to digastric digastric meaning that it has two gastric.
• It allows muscle above and beolw to be controlled. the structure anchors to some other muscles.
• stylohyoid.
• lesser horns.
• greater horns
• Suprahyoid Muscles.

Each bone Vertebrae

• cervical ( c1- 7)
• thoracic T1-12)
• lumbar.
• Sacral - merged
• The coccyx
• Body has the arch - is where the spinous and transverse process are at.
• spinous process.
• transverse process.
• seven process . ( one spin two trans and one accuate= total of seven)

Thoriac area.

• 12 pairs of ribs
• T1 with T12.
• vertebrae with spinal cord.
• - Sternum- front
  -

Ribs True vs False Rib

• true rubs 1-7.
• False rib 8 -12.
• Fourteen ri Eleven and twelves

Appendicular Skeleton -Top and bottom side parts .

• clavicle .

• Scapula back plate.

  • -Humerus - The top arm bone.
  • -Ulna - The bones on inner elbow.
  • - Radius - The bone side near the thumb outer.
  • -Carbons - The small inner wrist bones.
  • -metacarpals- The palm area below.
  • -Phalanges- The finger bones.

• femur - Top thigh bone .

• Patella The knee bone area near knee.

• Tibia - Th Lower bone area

• -Fibula- the outer side bone but still lower area.

• - tarsals- The bones of the foot below

• -metatarsals - Below the foot but still above the lower bone.

• -Front - Above the metatarsals and the toe area.

clavicle. - Attach to both the sternum

• sternoclavicular joint.
• scapula the acromion prosses to clavicular joint.
• The front one is coracoid process= the side.The Acromion = side to back corner.

Front view, shoulder, the glenoid cavity.

• Humerus features.

• laser tubercle.- the rough side area

• greater tubercle - The outer rough back area.

• intertubercle Feature : the spot for tendons

• deltold tuberosity

• Radial Groove - The bone area near both redius.

• Surgica neck- Top end of the arm but not forehead .It the the doctors area.

• cartilage is where both cartliage has been smoothed in

• Capituiums- The front lower wrist

• The elbow back bone, and both area.

• The elbow back bone. is the olecranon fossa

ulnar, The middle feature is the olecranon process

• the radius the trochlear of the humerus.

humorus top view: Humerus features

• Attaching to join of humerus shoulder.
• clavicle shoulder bones.

The Elbow bones. (Humerus ulna radius )

• humerus bone and the Ulna is the bones .
• trachea - is that of bone humorus.
• olecranon protect by by by this process bone.

The forearm is where Ulnar Radius are attached:

• proximal - near to.
• Distal- far away.
• the membrane that attach both is called interosseous membrane. - where they were hold each other

the forearm

• olecranon - that is attached to end bone.

Hand Area wrist

• radial Radial Radial dis end.
• radius joint - The cartilage the carpals connect with to form the radial with the radious bone.

HAND BONES

• 8 area bones.
  -Scaphoid
  -Lunate = where the bone connect with
  -Carpels-
  -Metacarpel
  -Fingerbones has three - flanges , three segments,
  proximal flange