Skeletal Physiology

Bone Homeostasis

Bones have 5 different function to help keep homeostasis. Support, Protection, Movement, Mineral Storage, and Hematopoiesis.

· Support – Bones are the framework of the body. They help keep shape and alignment of the body.

· Protection- The bones help protect different organs in the body such as the skull with the brain and ribs with the heart and lungs.

· Movement – Without bones the muscles couldn’t attach to anything. The bones act as levers to help movement. When the muscles retract they move the bone at the joint.

· Mineral Storage- Bones serve as a “Bank” for certain minerals like calcium, phosphorus, and other minerals. Blood calcium levels highly depend on the calcium movement rate between the blood and bones.

· Hematopoiesis – Blood cell formation is a process carried by red bone marrow. In adults, they’re located in the ends of long bones, skull, pelvis, and the ribs.

Intramembranous and Endochondral Ossification are made in two different ways. The intramembranous ossification takes place in a connective tissue membrane. They create Osteoblasts. Clusters of them are called centers of ossification. They release matrix material and collagenous fibrils. Eventually, Calcification of the organic bone matrix will occur when complex calcium salts are deposited. Endochondral ossifications are formed in cartilage models. Bone is deposited by osteoblasts which different from cells on the inner surface of the periosteum. When a blood vessel enters the rapidly changing cartilage model at the midpoint of the diaphysis.

Bone fracture repair is a process by which the body heals the tissues and removes the dead bone. The repair process is initiated by vascular damage. The body will either remove dead bone or use it to hold a repair tissue called a “Callus” in place. Fractures cause hemorrhage or pooling of blood at the injury. The blood clot is called a fracture hematoma. If the fracture is aligned and immobilized the callus tissue will model and be replaced with bone. Vitos is a skeletal repair material that consists of calcium and a sponge like matrix. It helps the callus immobilize the fracture and helps it receive nutrients. Then soon it will all be replaced with actual bone and be fixed.

Compare the classification of joints according to both structure and function.

- There are Fibrous Joints and Cartilaginous Joints. There are three types of Fibrous Joints the Syndesmoses joint, the sutures joint and the Gomphoses joints. There are two types of Cartilaginous Joints the Synchondroses joint and the Symphyses joint.

Some examples are-

· Syndesmoses Joints are between distal ands of radius and ulna

· Sutures Joints are between the skull bones

· Gomphoses Joints are between roots of teeth and jaw bone

· Synchondroses are the costal cartilage attachments of first rib to sternum

· Symphyses are the joints between bodies of vertebrae

-The structures of the Cartilaginous Joints are more about articulating bones and the Fibrous Joints structures are more towards the connecting bone and roots.

13. Identify the types of movement at synovial joints and give examples of specific joints where each occurs

- There are 3 types of Synovial joints the Uniaxial, Biaxial and Multiaxial

- Uniaxial are the Hinge and Pivot

- Biaxial are the Saddle and Condyloid

- Multiaxial are the Ball and Socket, and Gliding

Movements:

Hinge- around one axis only, flexion and extension only, ex. Elbow joint

Pivot- around one axis only, rotation, ex. Joint between first and second cervical vertebrae

Saddle- around two axes, flexion and extension, ex. Thumb joint between metacarpal and carpal bone

Condyloid- around two axes, flexion, adduction in other plane, ex. Joint between radius and carpal bone

Ball and Socket- around many axes, widest range of movements, ex. Shoulder joint

Gliding- around many axes, gliding movements, ex. Joints between carpal and tarsal bones

1. Identify each of the major constituents of bone as a tissue and discuss how structural organization contributes to function.

· Composition of bone matrix

-inorganic salts: are needle like crystals, they are oriented in the microscopic spaces between the collagen fibers in the bone matrix so that they can most effectively resist stress and mechanical deformation.

-organic matrix: the organic matrix of bone and other connective tissues is a composite of collagenous fibers and an amorphous mixture of protein and polysaccharides called ground substance. The ground substance of bones provide support and adhesion between cellular and fibrous elements and also serves an active role in many cellular metabolic functions necessary for growth, repair, and remolding.

· Compact bone

- compact bone: contains many cylinder shaped structural units called osteons , or haversian systems. There are four types of structures that make up the haversian system.

-First type is: lamellae_-_concentric, cylinder shaped layers of calcified matrix.

-Second type is: lacunae_-_Latin for “little lakes” small spaces containing tissue fluid in which bone cells lie imprisoned between the hard layers of the lamellae.

-Third type is: canaliculi _-_ ultra small canals radiating in all directions from the lacunae and connecting them to each other and into a larger canal, known as the heversian canal.

-Fourth type is: haversian canal_-_extends lengthwise through the center of each haversian systems; contains blood vessels, lymphatic vessels, and nerves from the haversian canal; nutrients and oxygen move through canaliculi to the lacunae and their bone cells- a short distance of about 0.1 mm or less.

2. Identify by name and discuss each of the major components of a Haversian system.

compact bone: contains many cylinder shaped structural units called osteons , or haversian systems. There are four types of structures that make up the haversian system.

-First type is: lamellae_-_concentric, cylinder shaped layers of calcified matrix.

-Second type is: lacunae_-_Latin for “little lakes” small spaces containing tissue fluid in which bone cells lie imprisoned between the hard layers of the lamellae.

-Third type is: canaliculi _-_ ultra small canals radiating in all directions from the lacunae and connecting them to each other and into a larger canal, known as the heversian canal.-Fourth type is: haversian canal_-_extends lengthwise through the center of each haversian systems; contains blood vessels, lymphatic vessels, and nerves from the haversian canal; nutrients and oxygen move through canaliculi to the lacunae and their bone cells- a short distance of about 0.1 mm or less.

3. List and describe the function of the three major types of cells found in bones.

· The three major types of cells are found in bone : osteoblasts (bone-forming cells) , osteoclasts (bone-reabsorbing cells), and osteocytes (mature bone cells). All bone surfaces are covered with continuous layer of cells that is critical to the survival of bone.

-The osteoblasts are small cells that synthesize ans secrete a specialized organic matrix, called osteoid, that is an important part of the ground substance of bone.

-osteoclasts are giant multinucleate cells that are responsible for the active erosion of bone minerals, they are formed by fusion of several precursor cells and contain large numbers of mitochondria and lysomes.

-osteoblasts are mature non dividing osteoblasts that have become surrounded by matrix and now lie within lacunae.

Hyaline Cartilage - provides firm support with some pliability. It covers the ends of the long bones as articular cartilage , providing springy pads that absorb compression at joints . Has resilient cushioning properties ; resists compressive stress. Supports the tips of the nose , connects the ribs to the sternum , and supports most of the respiratory system passages. The skeletal hyaline comes during childhood as the epiphyseal plates , provide for continued growth in length. Covers the ends of long bones in joint cavities ; forms costal cartilages of ribs , nose , trachea , and larynx.

Elastic Cartilage - Found where strength and exceptional stretch ability are needed. Elastic cartilage forms the skeletons of the external ear and the epiglottis. Maintain the shape of a structure while allowing great flexibility.

Similar to hyaline but more elastic fibers in matrix.

Fibrocartilage- Compressible and resists tension well , found where strong support and the ability to with strand heavy pressure are required. EX: the spongy cartilage of the knee , Intervertebral discs Strength with the ability to absorb compressive shock.

Less firm than the hyaline; thick collagen fibers predominate.

11) Growth of Cartilage

Interstitial Growth: The cartilage cells within the substance of the tissue mass divide and begin to secrete additional matrix. Internal division of chondrocytes is possible because of the soft, pliable nature of cartilage tissue. This type of growth is mostly seen during childhood and early adolescence, when the majority of the cartilage is still soft and capable of expansion from within

Appositional Growth: This occurs when chondrocytes in the deep layer of the perichondrium begin to divide and secrete additional matrix. The new matrix is then deposited on the surface of the cartilage, causing it to increase in size. This type of growth is unusual in early childhood but, once it starts it continues beyond adolescence and throughout an individual’s life.

12) Classification of joints

Joints are classified into 3 major categories using a structural or a functional scheme. If a structural classification is employed, joints are named according to the type of connective tissue that joins the bones together, (fibrous and cartilaginous) or by the presence of a fluid-filled joint capsule. (synovial joints)

If a functional classification scheme is used, joints are divided into three classes according to the degree of movement they permit. (synarthroses, amphiarthroses, and diarthroses) (Immovable, slightly movable and freely moveable)

Fibrous joints are synarthroses. The articulating surfaces of these joints fit closely together.

The three types of fibrous joints are: Syndesmoses- Joints on which fibrous bands connect two bones Sutures- Found only in the skull, teeth like projections jut out from adjacent bones and interlock with each other with only a thin layer of fibrous tissue between them. Gomphoses: unique joints that occur between the root of a tooth and the alveolar process of the mandible and maxilla.

Cartilaginous Joints are amphiarthroses: The bones that articulate to form a cartilaginous joint are joined together by either hyaline cartilage or fibrocartilage. There are two types of these

Sychondroses: Joints that are characterized by the presence hyaline cartilage between articulating bones Symphyses: a joint in which a pad or disk of fibrocartilage connects two bones

Synovial joints are diarthroses They are the body’s most moveable, numerous and the most anatomically complex joints. Seven types of structures for synovial joins joint capsules, synovial membrane, articular cartilage, joint cavity, menisci (articular disks), ligaments and bursea

Synovial joints are divided into three main groups: Uniaxial, biaxial, and multiaxial

Uniaxial joints: Synovial Joints that permit movement around only one axis and in only one plane. EX: Hinge Joints and Pivot Joints

Biaxial joints: Diaphroses that permit movement around two perpendicular axes in two perpendicular planes EX: Saddle Joints and Condyloid Joints

Multiaxial Joints: Joints that permit movement around three or more axes and in three or more planes EX: Ball and Socket joints and Gliding joints

1. List the four types of bones and give examples of each1. Long Bones --- Femur is a good example.2. Short Bones -- Carpals.3. Irregular bones -- vertebrae.

4. Flat bones -- The bones of the skull are a prime example.5. Sesamoid bones -- High-stress bones encased in tendons, connective

tissue, etc. Kneecaps are an example. 2. Identify the six major structures of a typical long bone.

1. Long bones have greater length than width and consist of a shaft and a variable number of endings (extremities).

2. They are usually somewhat curved for strength.3. Examples include femur, tibia, fibula, humerus, ulna and radius.4. Articulatory (or articular) cartilage reduces friction and absorbs shock at

freely moveable joints. 5. Endosteum is the membrane that lines the cavity of a bone. 6. Periosteum is a tough fibrous membrane that surrounds the outside of

bones wherever they are not covered by articulatory cartilage. 7. In adults the medullary cavity contains fatty yellow bone marrow.

3 Collective Questions

http://www.ehow.com/facts_5847486_changes-skeletal-system-due-age.html

•Cancer treatment may generate a need for a bone marrow transplant. Osteoporosis is a condition characterized by an excessive loss of calcium in bone. These 2 conditions are disruptions or failures of 2 bone functions. Identify these 2 functions and explain what their normal function should be.

The lack of bone marrow in Osteoporosis is because of the lack of function from the bone to make enough bone marrow, as compared to bone cancer, which compromises the ability of the bone to make healthy bone marrow.

•Explain why a bone fracture along the epiphyseal plate may have serious implications among children and young adults.

The Epiphyseal plate is located near the head of the epiphyseal bone and the reason a fracture among the plate would be cause for concern in young adults and children is because of the function of the epiphyseal plate. As a person grows, the plate of cartilage develops in to a line of bone. If a person were to be severely injured while growing, growth could be stopped, causing the child to be shorter than they were intended to grow.

•During the aging process, adults face the issue of a changing skeletal framework. Describe these changes and explain how these skeletal framework changes affect the health of older adults.

The changes of skeletal framework could affect people greatly as they progress in to older age these include bone density loss, spine and feet compressing and becoming weaker, and joints becoming less flexible.