5 Function of the Skeletal System
- Support
- Mineral Storage
- Blood Cell Production
- Protection
- Leverage
Support (Functions of the Skeletal System)
Framework for attachment of soft tissues and organ.
Mineral Storage (Functions of the Skeletal System)
Calcium and phophate ions
Blood Cell Production (Functions of the Skeletal System)
Red Bone Marrow produces RBCs, WBCs, and platelets
Protection (Functions of the Skeletal System)
Delicate tissues and organs are often surrounded by skeletal elements. The ribs protect the heart and lungs, the skull encloses the brain, the vertebrae shield the spinal cord, and the pelvis cradles delicate digestive and reproductive organs.
Leverage (Functions of the Skeletal System)
Many bones act as levers (rigid structure) that skeletal muscles pull on (generate force) to move the body with strength and efficiency.
Periosteum
- Superficial connective tissue of bone
- Highly vascular (rich blood supply)
- Anchored to the bone’s matrix by collagen bundles called perforating fibers or Sharpey’s fibers.
- Double Layered
Superficial Connective Tissue of Bone (Periosteum)
- Double layered
- Covers a bone’s external surfaces (except where articular cartilage is present)
Double Layered (Periosteum)
- Outer Layer
- Tough, Fibrous, and Protective
- Dense irregular connective tissue
- Collagen (Strength)
- Inner Layer
- Contains two mature bone cell types:
- Osteoblasts
- Osteoclasts
- Together, these two cells participate in bone remodeling: the constant “recycling” of bone matrix to maintain health of the bone.
- Contains two mature bone cell types:
Osteoblasts
Secrete new bone matrix
Osteoclasts
Secrete enzymes that digest bone matrix
2 Types of Osseous Tissue
- Compact (Cortical) Bone
- Spongy (Cancellous) Bone
Compact (Cortical) Bone
- Located immediately deep to periosteum
- Hard, dense (“compact”) tissue
- The strong shelll of the bone
Spongy (Cancellous) Bone
- Located inside the bone, deep to compact bone
- Hard matrix, but contains large spaces (“spongy”)
Compact Bone Tissue Structure (9)
- Osteon
- Lamellae
- Central Canal (Haversian Canal)
- Endosteum
- Osteoblasts
- Osteocytes
- Lacunae
- Canaliculi
- Perforating (Volkmann’s) Canals
Osteon
- Repeated, cylindrical unit of compact bone
- Concentric layers (Lamellae) of bone matrix, surrounding a central canal (Haversian Canal)
- Lacunae are found between the lamellae
- Little spaces, each containing an osteocyte
Lamellae
The concentic layers of bone matrix that surround the central canal.
Central Canal
Longitudinal canal in the center of an osteon that contains blood vessels and nerves.
- Contains blood vessels, nerves
- Supplies O2 and nutrients to osteocytes in the osteon; carries CO2 and other wastes away.
Endosteum
An incomplete cellular lining on the inner (medullary) surfaces of bones.
- Lines each central canal
- Like periosteum, contains osteoblasts and osteoclasts.
Osteocytes
What osteoblasts become when “trapped” by the bone matrix they secreted.
Lacunae
- Found between the lamellae
- Little spaces, each containing an osteocyte
Canaliculi
Tiny ECF-Filles canals that interconncet osteocytes with each other and the central canal
Perforating (Volkmann’s) Canals
- Carry blood vessels from periosteum to the osteons
- Run perpendicular to the osteons
Spongy Bone Tissue Structure
- Does not for osteons!!!
- Instead, grows in lattice-like formations called trabeculae
- Trabeculae
- Endosteum
- Osteoblasts
- Osteocytes
- Lacunae
- Canalculi
- Red Bone Marrow
- Yellow Bone Marrow
Trabeculae
Structure:
- Coveredf by endosteum (With osteoblasts, osteoclasts)
- Internal lamellae with osteocytes inside lacunae
- Spaces between trabeculae are filled with red and yellow marrow
Red Bone Marrow
Blood Cell Production
Yellow Bone Marrow
Adipose Tissue
Flat Bones
Have thin roughly paralellel surfaces. Flat bones form the roof of the skull, the sternum, the ribs, and the scapulae. They provide protection for underlying soft tissues and offer an extensive surface area for the attachment of skeletal muscles.
Sutural Bones
Or Wormian Bones, are small, flat, irregularly shaped bones between the flat bones of the skull, There are indivdual variations in the number, shape, and position of sutural bones. Their borders are like pieces of a jigsaw puzzle, and they range in size from a grain of sand to a quarter.
Long Bones
Are relatively long and slender. They are located in the arm and forearm, thigh and leg, palms, soles, fingers, and toes. The femur, the long bone of the thigh, is the largest and heaviest bone in the body.
Irregular Bones
Have complex shapes with short, flat, notched, or ridged surfaces. The spinal vertebrae, the bones of the pelvis, and several skull bones are irregular bones.
Sesamoid Bones
Are generally small, flat, and shaped somewhat like a sesame seed. They develope inside tendons and are most commonly located near joints at the knees, hands, and feet. Everyone has sesamoid patellae, or kneecaps, but indivdual s vary in the location and abundance of othe sesamoid bones. This variation, among others, account for disparities in the total number of bones in the skeleton. (can form in at least 26 locations)
Short Bones
Small and boxy. Examples od short bones include bones in the wrists (carpal bones) and in the ankles (tarsal bones).
Inorganic Component of Bone
The inorganic component of bone is the *mineral* component - a form of Calcium Phosphate called hydroxyapatite.
Organic Component of Bone
The organic component of bone is the cells and extracellular matrix (e.g. collagen).
Collagen
a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of vertebrates.[1] It is the main component of connective tissue, and is the most abundant protein in mammals,[2] making up about 25% to 35% of the whole-body protein content. Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendons, ligaments and skin, and is also abundant in corneas, cartilage, bones, blood vessels, the gut, and intervertebral discs. The fibroblast is the most common cell which creates collagen.
Hydroxyapatite
a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. Hydroxylapatite is the hydroxyl endmember of the complex apatite group. The OH- ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system. Pure hydroxylapatite powder is white. Naturally occurring apatites can, however, also have brown, yellow, or green colorations, comparable to the discolorations of dental fluorosis.
