Tuesday, August 17, 1999

Structure and Function of the Human Body week 3

Bone is a very active tissue. Please explain the pathway of how the bone cells get nutrients and oxygen from the blood vessels using the following terms: Periosteum, endosteum, lacunae, lamellae, canaliculi, perforating canals, osteon, Haversian canal (central canal) and trabeculae.
There are two types of bone tissue, compact bone (solid dense) and spongy bone (bone separated by spaces). Example, the humerus bone consists of compact bone (diaphysis and spongy bone) at each end or epiphysis. The periosteum is the outer layer of the bone where tendons and ligaments are attached; whereby, attaching muscle to bone and bone another. The main function of periosteum isolates bones to surrounding tissues provides a route to circulatory and nervous supply. It has an influence of growth and repair of the bone. The endosteum is found in the inner surface of the bone. The function of the endosteum is growth and repair of the bone. In compact bones, the functional unit is the osteon. Within the osteon, the bone cells (osteocytes) are layered around a central canal called haversian that contains some blood vessels. The bone cells are found in small pockets called lacunae which are found between calcifid matrix which is called lamellae which are cylindrical. The inter-connections inside the matrix have small channels called canaliculi that connect the lacunae with the nearby blood vessels. Nutrient and waste products are exchanged from the osteocytes through diffusion in the extracelluar fluid that surround the cells. Perforating canals provide a highway and linkage from the central canal to the periosteum and the marrow cavity.
In the spongy bone, has no osteons. Instead, the spongy bone consists of trabeculae which are lamellae that are shaped as thin rods that create an open network. Nutrients and waste are diffused between marrow and ostreocytes through small channels (canaliculi) that extend from the lacunae of the spongy bone end, where the triabeculea is exposed.

There are three main types of canals including canaliculi, Haversian canals and Volkmann's canals.

The canaliculi would join osteocytes. Second, the thicker canals are Haversian canals. In the center of the osteone are longitudinal directly through the bone. Third, the transverse tunnels are Volkmann canals. The Volkmann canals will go into the bone from the exterior; therefore, allowing vascularization to go into the osseous tissue.

Bone tissue being hard, it requires canals or tunnels to get the osteocytes nutrients to the cells. Osteocytes have long protrusions of their cytoplasm within the tunnels that contact other osteocytes. The Osteocytes are connected at these unions which can transport nutrient.
In general compare and contrast the three functional classifications of joints according to movement. What are two characteristics that make synovial joints unique and different from other joints? Which joint is stronger-the shoulder or hip joint and why is it?

Two characteristics that make synovial joints unique is they are found at the end of long bones. They are also unique in that they have fibrous joint capsule surrounding it. The hip joint is stronger, because the femur is the largest bone in the body and the hip joint was made for strength and stability. In comparison the shoulder has a higher range of movement; therefore, is weaker at the joint. (pg 174)

Please explain how the muscle cell’s anatomy of the cytoplasm is unique from other cells.
Cytoplasm has cytosol, which is dissolved in nutrients, ions, soluble, and insoluble proteins. Cytosol would contain higher concentration of potasiums ions and lower sodium ions. Likewise, extracellular fluid contains lower potassium-ion concentration. Cytosol contains high concentration of dissolved proteins like enzymes which regulate metabolic operations. It gives the cytosol it's consistency. Organelles directly connect to Cytosol. pg 72.
With your knowledge of how a muscle cell contracts please describe three mechanisms (problems) that could inhibit or disrupt the process of muscle contraction. Think about the process and the steps involved in muscle contraction.
The three mechanism are Concentric Contractions, Eccentric Contractions, Isometric Contraction. Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten or remain the same. Although the term contraction implies shortening, when referring to the muscular system, it means muscle fibers generating tension with the help of motor neurons.
Many sarcomeres work serially and in parallel to achieve the full contraction ability of the muscle. The sarcomere includes Actin and Myosin. Actin and Myosin are protein based filaments from opposite sides of the sarcomere. Once the muscle is at rest, both the Actin and myosin filaments overlap. When the muscle contracts, the filaments from the opposing sides slide so the pulling both walls of the sarcomere. When the muscle is fully contacted, the filaments overlap each other the most. The sliding motion is activated by calcium that floods the sarcomeres (at the end of a process that is triggered by a command from a motor nerve). The calcium reveals sites on the Actin filaments at which molecular 'whips' extending from the Myosin filaments, can throw themselves, attach, pull, and leave, using the muscle's energy reserves in the process. Each molecular whip works at its own time (much like cylinders in an internal combustion engine), so that in any given time, contact between the filaments is being made by some of the whips.
What is the difference between osteoarthritis and osteoporosis?
Osteoarthritis is a noninflammatory condition that occurs in obese people or people who have trauma joints. They are both over the age of 65. It has lost of cartilage and adjacent bone overgrowth. Osteoporosis is a metabolic condition with loss of trabecular bone. Osteoporosis normally happens in women over 65, because she had steroids, smoking, caffeine, thyroid replacement. The hip and vertebral fracture are at risk for women. (Krant, J, Healthcentral, 2006)

No comments :