Anatomy and Physiology PDF

Chapter 5: The Skeletal System Cartilages Ligaments Skeletal System The skeleton is divided into two parts What...

Chapter 5: The Skeletal System Cartilages Ligaments Skeletal System The skeleton is divided into two parts What (subdivisions) ○ The skeletal system is the 1. Axial Skeleton internal frame of the body and a. Bones that form the includes bones, cartilages, longitudinal axis of the body joints, and ligaments b. Mostly immovable and not How articulated ○ In addition to providing c. Skull down to pelvic gurgle structure, bones articulate, or come together, at joints to 2. Appendicular Skeleton allow body movement a. The bones of the limbs and Why girdles that attach them to the ○ The skeletal system is essential axial skeleton to producing organs, b. Movable, articulated producing blood cells, storing c. Arms, legs, plantar (soul of ur essential minerals, and feet); jointed area anchoring skeletal muscles so (Joints give these parts of the skeleton flexibility that their contractions cause and allow movement to occur) body movements. Skeleton ➔ Comes from the Greek word – “dried up body” ➔ Strong yet light ➔ Adapted for its functions of protecting the body and allowing motion ➔ No other animal has such long legs (compared to the arms and forelimbs, or such a strange foot, and few have grasping hands with opposable thumbs Functions of Bones The bones of the skeleton - Besides contributing to body structure, Are part of the skeletal system our bones perform several important Which includes joints, cartilages and body functions. ligaments (fibrous cords that bind the - Support the body bones together at joints) - Protect soft organs - Movement Parts of the Skeletal System - Store mineral and fats Bones (Skeleton) - Blood cell formation (hematopoiesis) Joints  - Hema = related to something for muscles to contract, and for blood about the blood to clot. Problems occur not only when - Hematopoiesis = new there is too little calcium in the blood, formation or regeneration of but also when there is too much. blood cells Hormones control the movement of - Stem cells in bone marrow are calcium to and from the bones and the first steps of blood cells blood according to the needs of the body. Indeed, “deposits” and a. Support = Bones, the “steel frame” of “withdrawals” of calcium (and other the body, form the internal framework minerals) to and from bones go on that supports the body and cradles its almost all the time. soft organs. The bones of the legs act as pillars to support the body trunk when e. Blood Cell Formation = Blood cell we stand, and the rib cage reinforces the formation, or hematopoiesis thoracic wall. (hem″ah-to-poi-e′sis), occurs within the marrow cavities of certain bones. b. Protection = Bones protect soft body organs. For example, the fused bones of Classification of Bones the skull provide a snug enclosure for - The adult skeleton is composed of 206 the brain, allowing someone to juggle a bones soccer ball with their head without worrying about injuring the brain. The 2 Types of Osseous / Bone tissue (Basic types of vertebrae surround the spinal cord, and bones) the rib cage helps protect the vital 1. Compact Bone = dense and looks organs in the thorax. smooth and homogeneous a. several calcium ions or salts c. Allow movement = Skeletal muscles, are deposited there which is attached to bones by tendons, use the why they are hard bones as levers to move the body and its parts. As a result, we can breathe, 2. Spongy Bone = spiky, open appearance walk, swim, and throw a ball. like a sponge a. It's not soft, it's just porous d. Storage = Fat is stored in the internal b. The holes of haversian canals (marrow) cavities of bones. Bone itself contain blood vessels just like serves as a storehouse for minerals, the spongy bones; allows the blood most important of which are calcium vessels to pass through and phosphorus. Most of the body’s calcium is deposited in the bones as calcium salts, but a small amount of 2+ calcium in its ionic form (Ca ) must be present in the blood at all times for the nervous system to transmit messages,  Long bones - Typically longer than they are wide - As a rule, they have a shaft with enlarged ends (because this is where the calcium salts are deposited) - Mostly compact bone; also contains spongy bone at the ends - Inside is hollow where u find the bone marrow - All the bones of the limbs, except the Bones come in many sizes and shapes patella (kneecap) and the wrist and The tiny pisiform bone of the wrist = ankle bones, are long bones size and shape of a pea - Example: Femur, Humerus Femur, or the thigh bone = nearly 2 feet long and has a large, bell-shaped head Bones are classified according to shape into 4 groups a. Long b. Short c. Flat d. Irregular Flat bones - Thin, flattened, and usually curves - Two thin layers of compact bone sandwich a layer of spongy bone between them - Most bones of the skull, the ribs and the sternum (breastbone) are flat bones - Example: - Most bones of the skull - Ribs - Sternum Irregular Bones Short bones - Do not fit one of the proceeding - Generally cube-shaped and contain categories mostly spongy bone with an outer layer - The vertebrae, which make up the of compact bone spinal column - Bones of the wrist and ankle are short - Like short bones, they are mainly bones spongy bone with an outer layer of - Sesamoid bones, a type of short bone, compact bone which form within tendons, are a - Examples: Vertebrae, hip bones special type of short bone (patella) - Best known example is the patella - Examples: Carpals (Wrist bones), tarsals (ankle bones) Gross Anatomy of a Long Bone - Composed of compact bone Periosteum - In a long bone, the diaphysis, or shaft - Outside covering of the diaphysis makes up most of the bone’s length - Fibrous connective tissue membrane and is composed of compact bone - Perforating (sharpey’s) fibers secure - The diaphysis is covered and protected periosteum to underlying bone by a fibrous connective tissue - Entire surface of bone as covering membrane, the periosteum - In the distal ends, you’ll find highest - Hundreds of connective tissue fibers, amounts of friction which is why you called perforating fibers, or Sharpey’s have articular cartilage (they have fibers, secure the periosteum to the overlapping fibers of elastic and underlying bone collagen fibers) so they are stronger than ur fibrous connective tissue The holes where the blood vessels are passing through is your haversian canal Articular cartilage (Hyaline cartilage) - Covers the external surface of the epiphysis - Made of hyaline cartilage - Decreases friction at joint surfaces Epiphysis - articular cartilage is glassy hyaline - Ends of long bones cartilage, it provides a smooth surface - Composed spongy bone that decreases friction at the joint when - Each epiphysis consists of a thin layer covered by lubricating fluid. of compact bone enclosing an area (Proximal is on top, and distal is below) filled with spongy bone Diaphysis (Shaft) - Makes up most of the bone’s length - The longest part - Where you’ll find the hollow part  epiphyses of long bones such as the Epiphyseal Line humerus and femur. - Remnant of the epiphyseal plate - Seen in adult bones - In adult bones, there is a thin line of bony tissue spanning the epiphysis that looks a bit different from the rest of the bone in that area. Epiphyseal plate - Belongs to someone who is still growing - Flat plate of hyaline cartilage seen - Young, growing bone - Once you reach the end of puberty, you Bone marking won't see epiphyseal plate anymore, - Even when looking casually at bones, only the epiphyseal line you can see that their surfaces are not - Epiphyseal plates cause the lengthwise smooth but scarred with bumps, holes, growth of a long bone. By the end of and ridges. puberty, when hormones inhibit long - Irregularities of bone structure bone growth, epiphyseal plates have - Sites of attachment for muscles, been completely replaced by bone, tendons, and ligaments leaving only the epiphyseal lines to - Passages for nerves and blood vessels mark their previous location. - Causes lengthwise growth of a long Categories of bone markings bone Projections or processes – grow out from the bone surface Medullary Cavity ○ Terms often begin with T - The inner bony surface of the shaft is Depressions or cavities – indentations covered by a delicate connective tissue ○ Terms often begin with F called endosteum. (except facet) - In infants, the cavity of the shaft is a storage area for red marrow, which produces blood cells. - Children’s bones contain red marrow until the age of 6 or 7, when it is gradually replaced by yellow marrow, which stores adipose (fat) tissue. In adult bones, red marrow is confined to cavities in the spongy bone of the axial skeleton, the hip bones, and the Structure of Bone - Bone is relatively lightweight and resists tension and other forces - Organic parts (collagen fibers) of the bone make bone flexible and have great tensile strength - Calcium salts deposited in the bone In compact bone, the mature bone cells, make bone hard to resist compression osteocytes, are found within the bone matrix - Contributes to the hard texture in tiny cavities called lacunae. The lacunae are of the bones arranged in concentric circles called lamellae - Under a microscope, you can see that around central canals (also called Haversian spongy bone is composed of small Canals). Each complex consisting of a central needlelike pieces of bone called canal and matrix rings is called an osteon or trabeculae and lots of “open” space Haversian System, and is the structural and filled by marrow, blood vessels and functional unit of compact bone. Central nerves canals run lengthwise through the bony matrix, carrying blood vessels and nerves to all Microscopic Anatomy areas of the bone. Tiny canals, canaliculi, - The appearance of spongy bone and radiate outward from the central canals to all compact bone to the naked eye only hint lacunae. The canaliculi form a transportation at their underlying complexity. system that connects all the bone cells to the - Under a microscope, you can see that nutrient supply and waste removal services spongy bone is composed of small through the hard bone matrix. Because of this needlelike pieces of bone called elaborate network of canals, bone cells are well trabeculae and lots of “open” space nourished in spite of the hardness of the matrix, filled by marrow, blood vessels and and bone injuries heal quickly. The nerves communication pathway from the outside of the bone to its interior (and the central canals) is completed by perforating canals (also called cartilage “bones” enclosed by Volkmann’s canals), which run in the compact actual bone matrix. bone at right angles to the shaft (diaphysis) 2. In the fetus, the enclosed cartilage is and central canals. digested away, opening up a medullary cavity The calcium salts deposited in the matrix give - The enclosed hyaline cartilage bone its hardness, which resists compression. model is replaced by bone, and The organic parts (especially the collagen the center is digested away, fibers) provide for bone’s flexibility and great opening up a medullary cavity tensile strength (ability to be stretched without within the newly formed bone breaking). - Any word that has blasts means formation while clasts is Bone formation, Growth, and breakage Remodeling - Ossification is the process of bone formation - Occurs on hyaline cartilage models or fibrous membranes - Long bone growth involves two major phases The skeleton is formed from two of the strongest and most supportive tissues in the body—cartilage and bone. In embryos, the skeleton is primarily made of hyaline cartilage, but in young children, most of the cartilage has been replaced by bone. Cartilage remains only in isolated areas such as the bridge of the nose, parts of the ribs, and the joints. Two major phases of ossification in long bones 1. Osteoblasts (Bone-Forming cells) cover hyaline cartilage model with bone matrix - Hyaline cartilage model is completely covered with bone matrix (a bone “collar”) by osteoblasts By birth or shortly after, most cartilage is - As the embryo develops into a converted to bone except for two regions in a fetus, for a short period it has long bone  1. Articular cartilages = that cover the - Osteoblasts in the periosteum add bone ends bone matrix to the outside of the 2. Epiphyseal plates = elongates inside diaphysis - Osteoclasts in the endosteum remove In order for bones to increase in length, new bone from the inner surface of the cartilage is formed continuously on external diaphysis wall, enlarging the face (joint side) of these two cartilages medullary cavity Old cartilage (abutting the internal face of the - Because these two processes occur at articular cartilage and medullary cavity) is about the same rate, the circumference broken down and replaced by bony matrix of the long bone expands, and the bone widens Bone growth is determined / controlled by hormones, such as growth hormone and sex hormones (most important hormones) - It ends during adolescence, when the epiphyseal plates are completely converted to bone - Parathyroid hormones ensure you have sufficient calcium in your blood so it does not signal to break bones Bone Remodeling - Bone is a dynamic and active tissue Bones are remodeled continually in response to changes in 2 factors 1. The calcium ion level in the blood 2. The pull of gravity and muscles on the skeleton Calcium Ion Regulation - Parathyroid hormone (PTH) - Released when calcium ion levels in blood are low - Activates osteoclasts (bone destroying cells) How do bones widen? - Osteoclasts break down bone and release calcium ions into the blood Appositional Growth - Hypercalcemia (high blood calcium - Bones growth in width or increase in levels) prompts calcium storage to diameter  bones by osteoblasts (hyper means be broken down or formed so that the skeleton anything mataas or too much) can remain as strong and vital as possible. When the blood calcium ion level drops below its homeostatic level, the parathyroid glands (located in the throat) are stimulated to release parathyroid hormone (PTH) into the blood. PTH activates osteoclasts, giant bone-destroying cells in bones, to break down bone matrix and release calcium ions into the blood. When the blood calcium ion level is too high (hypercalcemia), calcium is deposited in bone matrix as hard calcium salts by osteoblasts. High calcium – calcitonin Bone remodeling Bone Fractures - Essential if bones are to retain normal proportions and strength during Bone Fracture long-bone growth as the body - We classify bones as connective tissues increases in size and weight so they are regenerate but with average - Also accounts for the fact that bones speed become thicker and form large projections to increase their strength in Fracture: Break in a Bone areas where bulky muscles are attached. - At such sites, osteoblasts lay down new Types of Bone Fractures matrix and become trapped within it. - Closed (simple) fracture is a break that (Once they are trapped, they become does not penetrate the skin osteocytes, or mature bone cells.) In - Open (compound) fracture is a broken contrast, the bones of bedridden or bone that penetrates through the skin physically inactive people tend to lose mass and to atrophy because they are no longer subjected to stress. The 2 controlling mechanisms – calcium uptake and release as well as bone remodeling – work together PTH determines when bone is to be broken down or formed in response to the need for If your long bones break in half in the middle, more or fewer calcium ions in the blood. The you need metal support or titanium (needs stresses of muscle pull and gravity acting on surgery) the skeleton determine where bone matrix is to Bone fractures are treated by reduction cells of various types form (realignment of the broken bones) and internal and external masses of immobilization (putting casts, stopping bones repair tissue, which collectively from moving; needs several weeks to attach form the fibrocartilage callus. again) The internal and external In Closed reduction: bones are manually masses, called calluses, coaxed into position by physician’s hands originate from cells of the - Does not need any surgery endosteum and periosteum, - Using the force to put it back to place respectively, and contain - Bone ends are secured together with several elements—cartilage pins or wires matrix, bone matrix, and - After the broken bone is reduced, it is collagen fibers—which act to immobilized by a cast or traction to “splint” the broken bone, allow the healing process to begin closing the gap. - The healing time for a simple fracture 3. Bony callus forms and replaces the is 6-8 weeks but is much longer for fibrocartilage callus large bones and for the bones of older a. Osteoblasts and osteoclasts people (because of their poor migrate in circulation) - As more osteoblasts and osteoclasts migrate into the Repair of bone fractures involves 4 major area and multiply, the events fibrocartilage callus is 1. Hematoma (blood-filled swelling, or gradually replaced by the bony bruise) is formed = deprive the bone of callus made of spongy bone nutrients; blood clasp 4. Bone remodeling occurs in response to - Blood vessels are ruptured mechanical stresses when the bone breaks - Over the next few weeks to - As a result, a blood-filled months, depending on the swelling, or bruise, called a bone’s size and site of the break, hematoma forms the bony callus is remodeled in - Bone cells deprived of response to the mechanical nutrition die stresses placed on it, so that it 2. Fibrocartilage callus forms forms a strong, permanent a. Cartilage matrix, bony matrix, “patch” at the fracture site. collagen fibers splint - Two early events of tissue repair are the growth of new capillaries (granulation tissue) into the clotted blood at the site of the damage and disposal of dead tissue by phagocytes. As this goes on, connective tissue Axial Skeleton It is divided into 3 parts 1. Skull 2. Vertebral Column 3. Thoracic cage