Skeletal PhysiologyGatlin Group B8

Fibrous Joint StructureThese types of joints are held together by fibrous connective tissue, no joint cavity is present. Either slightly mobile or immobile.

Synovial Joint StructureMade up of synovial fluid, freely movable and characterize most joints.Subtypes- Hyaline Cartilage- Covers the end of the boneSynovial Membrane- Surrounds synovial cavity.Fibrous capsule- Made up of ligaments ( dense, irregular connective tissue)Articulate capsule- Both synovial and fibrous membrane.

Types Of Movement SYNOVIAL JOINTS- All are freely movable (diarthrosis)Gliding- Two sliding surfacesHinge- Concave surface with convex surface, diathrosisPivot- Rounded end fits into ringCondyloid- oval condyle with oval cavitySaddle- each surface is concave or convexBall&Socket- Ball shaped head, and cup shaped pocket

Joint Types PicturesSynovial Fibrous Cartilaginous

The Four Types of Bones

● Long Bones● Short Bones● Flat Bones● Irregular Bones

Long BonesThese bones typically have an elongated shaft and two expanded ends one on either side of the shaft. The shaft is known as diaphysis and the ends are called epiphyses. Normally the epiphyses are smooth and articular. The shaft has a central medullary cavity where lies the bone marrow.

Examples include the humerus, femur, radius, ulna, tibia and fibula

Short BonesThese bones are short in posture and can be of any shape. Most of them are named according to their shape.

Examples of this class of bones include cuboid, cuneiform, scaphoid, trapezoid etc. In fact all the carpal and tarsal bones are included in this category.

Flat BonesThese bones are flat in appearance and have two prominent surfaces. They resemble shallow plates and form boundaries of certain body cavities.

Examples include scapula, ribs, sternum etc.

Irregular BonesThe shape of these bones is completely irregular and they do not fit into any category of shape.

Examples of this type of bones are vertebrae, hip bone and bones in the base of skull.

Major Structures of a Long Bone

● The diaphysis, or shaft, is the long tubular portion of long bones. It is composed of compact bone tissue.

● The epiphysis (plural, epiphyses) is the expanded end of a long bone. It is in the epiphyses where red blood cells are formed.

● The metaphysis is the area where the diaphysis meets the epiphysis. It includes the epiphyseal line, a remnant of cartilage from growing bones.

● The medullary cavity, or marrow cavity, is the open area within the diaphysis. The adipose tissue inside the cavity stores lipids and forms the yellow marrow.

● Articular cartilage covers the epiphysis where joints occur.● The periosteum is the membrane covering the outside of the diaphysis

(and epiphyses where articular cartilage is absent). It contains osteoblasts (bone-forming cells), osteoclasts (bone-destroying cells), nerve fibers, and blood and lymphatic vessels. Ligaments and tendons attach to the periosteum.

● The endosteum is the membrane that lines the marrow cavity.

The Typical Long Bone

Bone as a TissueThere are two different kinds of bone tissue: Compact and Spongy bone.Compact bone● Is made up of concentric rings of matrix that surround central canals which

contain blood vessels.● Embedded in this bone tissue are small cave-like spaces called lacunae,

which are connected to each other through small tunnels called canaliculi.● The lacunae contain osteocytes cells. As just discussed, osteocytes help

maintain healthy bone tissue and are involved in the bone remodeling process that will be outlined later in this lesson.

Spongy bone● Looks like an irregular latticework (or sponge) with lots of spaces

throughout.● These spaces are filled with red bone marrow which is the site of

hematopoiesis or formation of blood cells.

The Haversian SystemA Haversian System consists of many cylinder-shaped structural units. There are four types of structures that make up each Haversian system. (1)1. Lamellae – concentric, cylinder-shaped layers of calcified matrix2. Lacunae – small spaces containing tissue fluid in which bone cells lie imprisoned between the hard layers of the lamellae3. Canaliculi – ultrasmall canals radiating in all directions from the lacunae and connecting them to each other and into a larger canal, the haversian canal4. Haversian canal – extends lengthwise through the center of each Haversian system; 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.

Three Major Types of Cells Found in Bones

1. Osteoblasts – bone-forming cells2. Osteoclasts – bone-resorbing cells3. Osteocytes – mature bone cells

Osteoblasts

Osteoblasts are small cells that synthesize and secrete a specialized organic matrix, called osteoid. (1)

Osteoclasts

Osteoclasts are giant multinucleate cells that are responsible for the active erosion of bone minerals. (1)

OsteocytesOsteocytes are mature, non-dividing osteoblasts that have become surrounded by matrix and now lie within lacunae. (1)

Homeostatic Functions of Bones1. Support: contributes to the shape, alignment, and positioning of the body parts2. Protection: hard, bony “boxes” that serve to protect the delicate structures they enclose3. Movement: bones with their joints constitute levers, muscles are anchored firmly to bones, as muscles contract and shorten, they pull on bones. Making it movement in a joint4. Mineral storage: depends on changes in the rate of calcium movement between the blood and bones5. Hematopoiesis: blood cell formation(1)

Intramembranous and Endochondral bone

Intramembranous and Endochondral bone are two essential processes during fetal development of the mammalian skeletal system by which bone tissue is created

Intramembranous:· Cartilage is not present during intramembranous ossification· Intramembranous ossification is essential process during the natural healing of bone fractures and the rudimentary formation of bones of the head

Endochondral:· Cartilage is present during endochondral ossification· Essential process during the rudimentary formation of long bones, the growth of the length of long bones, and the natural healing of bone fractures.

Bone Fracture Repair1. White blood cells move in to the area to clean up debris created by

the break, which creates inflammation, in turn triggering the growth of new blood cells

2. New blood vessels develop to begin the healing process

3. Soft callus also known as cartilage or soft fibrous tissue, begins to form to bridge the gap from the break.

4. A harder cartilage develops in place of the soft cartilage, forming a more solid bond within the gap

5. Through a process called remodeling, old bone is continually replaced by new bone, completing the process of bone fracture healing.

Bone and Cartilage · A bone is a rigid organ that constitutes part of the endoskeleton of vertebrates. It supports and protects the various organs of the body, produces red and white blood cells and stores minerals. Bone is made up of osteoblasts, osteocytes, osteoclasts, and bone lining cells which regulate the movement of calcium· Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones. Cartilage is made up of chondroblasts, chondrocytes, and dense matrix made up of collagen and elastic fibers