Anatomy and Physiology

 

ANATOMY AND PHYSIOLOGY

 

Bones are rigid organs that constitute part of the endoskeleton of  of vertebrates. vertebrates. They support and protect the various organs of the body, produce red andwhite andwhite blood cells and store minerals. Bone tissue is a type of dense connective tissue. Bones come in a variety of shapes and have a complex internal and external structure, are lightweight yet strong and hard, and serve multi ple functions. One of the types of tissue that makes up bone is the mineralized osseous tissue, also called bone tissue, that gives it rigidity and a coral-like coral-like three-dimensional internal structure. Other types of tissue found in bones include marrow, endosteum, periosteum, nerves, blood vessels and cartilage. At birth, there are over 270 bones in an infant human's bod y, but many of these fuse together as the child grows, leaving a total of 206 separate bones in an adult. The largest bone in the human body is thefemur  the femur and and the smallest bones are auditory ossicles.

Bones have eleven main functions: Mechanical  

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Protection  —  bones can serve to protect internal organs, such as the skull protecting skull protecting the brain or the ribs protecting ribs protecting the heart and lungs.  lungs. 

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Structure bones provide a frame to keep the body supported. Movement —  bones, skeletal muscles, tendons, ligaments and joints function together to generate and transfer forces so that individual body parts or the whole  body can be manipulated in three-dimensional three-dimensional space. The interaction between bone and musc muscle le is studied in biomechanics. biomechanics.     Sound transduction  —  bones are important in the mechanical aspect of o vershadowed hearing.  hearing.  Synthetic  

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Blood production  —  the marrow, located within the medullary cavity of long bones and interstices of cancellous bone, produces blood cells in a process called hematopoiesis.  hematopoiesis.  Metabolic 

 

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Mineral storage  —  bones act as reserves of minerals important for the body, most notably calcium and phosphorus.  phosphorus.  Growth factor storage factor storage  —  mineralized bone matrix stores important growth factors such as insulininsulin-like like growth factors, transforming growth factor, bone morphogenetic proteins and others. Fat storage —  the yellow bone marrow acts as a storage reserve of fatty of fatty acids.  acids.  Acid-base Acid -base balance  balance —  bone buffers the blood against excessive pH changes by absorbing or releasing alkaline salts. salts.   Detoxification  —  bone tissues can also store heavy metals and other foreign elements, removing them from the blood and reducing their effects on other tissues. These can later be gradually released for excretion. for  excretion.[citation needed ] 

 

 

Endocrine organ  —  bone controls phosphate metabolism by releasing fibroblast growth factor  –   –  23 (FGF-23), which acts on kidneys to reduce  phosphate reabsorption. Bone cells also release a hormone called osteocalcin, which contributes to the regulation of blood of  blood sugar  sugar (glucose) (glucose) and fat deposition. deposition.   Osteocalcin increases both the insulin secretion and sensitivity, in addition to boosting the number of  of insulin-producing insulin-producing cells and reducing stores of fat. Mechanical properties[ 

The primary tissue of bone, osseous tissue, is a relatively hard and lightweight composite material. It is mostly made up of a composite material incorporating the mineral calcium phosphate in the chemical arrangement termed calcium hydroxylapatite (this is the osseous tissue that gives bones their rigidity) and collagen, an elastic protein which improves fracture resistance. It has r elatively high compressive strength of about 170 MPa (1800 kgf/cm²) kgf/cm²) but poor  poor tensile tensile strength of 104 –  121 MPa and very low shear stress strength (51.6 MPa), MPa), meaning it resists pushing forces well, but not pulling or torsional f orces. While bone is essentially brittle, it does have a significant degree of elasticity, of  elasticity, contributed chiefly by collagen. All bones consist of living and deadcells dea dcells embedded in the mineralized organic matrix that makes up the osseous tissue. Bone structure

Bone is not a uniformly s olid material, but rather has some spaces between its hard elements. Compact (corti cal) bone 

The hard outer layer of b ones is composed of compact of compact bone tissue, so-called due to its minimal gaps and spaces. Its porosity is 5 – 30%. 30%.[6] This tissue gives bones their smooth, white, and solid appearance, and accounts for 80% of the total bone mass of an adultskeleton. adultskeleton. Compact bone may also be referred to as dense bone. Tr abecular abecular (cancellous or spongy) spongy) bone 

Filling the interior of the bone is the trabecular bone tissue (an open cell porous network also called cancellous or spongy bone), which is composed of a network of  rod- and plate-like elements that make the overall organ lighter and allow r oom for blood vessels and marrow. Trabecular bone accounts for the remaining 20% of  total bone mass but has nearly ten times the surface area of compact bone. I ts porosity is 30 – 90%. 90%.[6] If, for any reason, there is an alteration in the strain the cancellous is subjected to, there is a rearrangement of the trabeculae. The microscopic difference between compact and cancellous bone is that compact bone consists of haversian sites and osteons, while cancellous bones do not. Also, bone surrounds blood in the compact bone, while blood surrounds bone in the cancellous bone.

Tibia and Fibula

The tibia and fibula are the two bones making up the pelvic limb distal to the patella and femur and proximal to the tarsals and metatarsals. The fibula is a very thin  bone in comparison to the tibia. Note the tibial crest, whic which h is unique to the tibia and he helps lps form the "triangular" shape of the bone. Also note the lateral and medial condyles of the tibia, the extensor sulcus, the medial malleolus, and the tibial tuberosity.