 The Skeletal System  Chapter 6-9

 Individual bones:  Tissues  Bone  Cartilage  Epithelial tissue  Fibrous connective tissue  Blood  Nervous tissue

 Bone Structure  Long bone  External structure  Epiphysis, the portion of the bone that interacts with other bones  Articular cartilage, protective layer of hyaline cartilage coating the epiphysis

 Hyaline cartilage, most common type of cartilage, looks like “milky glass”  Diaphysis, long narrow portion between epiphyses, AKA: shaft

 Periosteum, any part of the bone not covered by articular cartilage is protected by this tough fibrous membrane. It is a vascular tissue, functions in bone repair.

 Internal structure  Tissue types:  Compact bone, dense strong and resistant to bending

 Spongy bone, branching bony plates that create irregular spaces, strong and durable because they allow for some compression.

 Tissue location  Compact bone makes up the wall of the diaphysis

 Spongy bone makes up the bulk of the epiphysis especially in regions that are subject to compression, (weight bearing joints)

 Description: the diaphysis is a semi-rigid hollow structure  Medullary cavity, hollow tube runs from end to end in the open space of the diaphysis

 Endosteum, lines the cavity  Marrow, specialized, highly functional, soft CT, inside the cavity

 Microscopic Structure:  Osteocyte, individual compact bone cell, located in…

 Lacunae, chambers arranged in concentric circles around…  Osteonic canal, pathway for arteries, veins, and nerves through the bone

 Canaliculus, smaller canals running perpendicular to the osteonic canal, connecting lacunae

 Haversian System: (aka Osteon) the whole system of concentric circles and the canals associated with them

 Volkmann’s canals, contain larger vessels and nerves allowing for communication of entire Haversian systems, the medullary canal, and the bone surface.

 Spongy bone avoids this whole process, thin bony plates allow for nourishment by diffusion.

Development Should it be a choice?

Two means of bone formation: 1.Intramembranous bone formation 2.Endochondral bone formation

Intramembranous Bone Broad, flat bones of the skull Formation –Osteoblasts become active and spongy bone is formed throughout existing membrane. –Left over membrane becomes periosteum.

Endochondral Bone Most long bones Formation: –Masses of hyaline cartilage develop rapidly giving even the young fetus a “human” structure.

–Ossification is a gradual process The center of the medullary cavity serves as the primary ossification center. Ossification occurs from the inside out.

The secondary ossification center is formed later in the open space of the epiphysis. This ossification also occurs in an outward direction.

–Between the two ossification centers there is an epiphyseal disc (AKA growth plate)

–Bone formation, lengthening continues until the two ossified areas meet.

Bone Demolition Osteoclasts break down bone tissue

Remodeling Osteoblasts form new bone tissue for replacement and remodeling.

Gross Function Provide shape Support Protection Provide structure Serve as storage units Aid in body movement Blood cell formation

Movement Gross movement

4 Parts of a Lever 1.Rod (bar) 2.Fulcrum (pivot) 3.Resistance ( weight being moved. 4.Force (energy supplying movement)

Example 1.Rod: radius and ulna 2.Fulcrum: elbow joint 3.Resistance: hand and object 4.Force: biceps brachii

What is the reverse? 1.Rod: radius and ulna 2.Fulcrum: elbow joint 3.Resistance: hand and object 4.Force: triceps brachii

What is happening? a. b. c. d. e.

Blood Cell Formation Hematopoiesis

Once upon a time… in the yolk sac hematopoiesis began for the embryo. Throughout life hematopoiesis continues in the …

Liver Spleen Bone marrow –Red marrow –(Yellow marrow)

Red Marrow Functions in the formation of: –RBC –WBC –platelets

Why is it red? Hemoglobin carried in RBC, changes the pigmentation of the marrow.

Yellow Marrow Functions in fat storage. Inactive in hematopoiesis. Replaces much of the red marrow as a human ages.

Why is it yellow? Fat in the body is yellow. Gooey, gross, and yellow.

Oh where oh where did the red marrow go? While most of the red marrow is replaced by yellow marrow, red marrow for hematopoiesis does remain in the spongy bone of the…

Thorax Vertebra Pelvis Epiphysis of the –Humerus –Femur

Bone as a Storage Unit Bone is used to store inorganic salts. (No Carbon) Primarily stores Ca+ [Ca+] control –If [Ca+] in blood is too low

osteoclasts are stimulated to breakdown bone tissue to release Ca+. –If [Ca+] in blood is too high, osteoblasts are stimulated to form bone tissue, trapping the Ca+.

Organization 2 major portions –Axial: head, neck, and trunk –Appendicular: limbs and anchoring parts

Axial 1.Skull: cranium and facial bones 2.Hyoid bone: between jaw and neck, helps tongue function

3.Vertebral column: back bone, series of bony vertebrae and cartilaginous intervertebral discs.

4.Thoracic cage: used to protect the organs of the thorax and upper abdomen.

Appendicular 1.Pectoral girdle: clavicle and scapula, the attachment site of the arm. 2.Upper limb: humerus, radius, ulna, carpals, metacarpals, phalanges.

3.Pelvic girdle: 2 coxal bones forming protection for lower organs and attachment site for legs. 4.Lower limbs: femur, tibia, fibula, patella, tarsals, metatarsals, phalanges.