Bone Development & Growth Processes PDF

zone reserve les adjacenttroa Presentation October 16, 2024  Grow in Length occurs at growth place The epiphyseal plate is the area of growth in length in a long bone. It...

zone reserve les adjacenttroa Presentation October 16, 2024  Grow in Length occurs at growth place The epiphyseal plate is the area of growth in length in a long bone. It is a layer of hyaline cartilage where ossification occurs in immature bones. On the epiphyseal side of plate, cartilage is formed. On the diaphyseal side, cartilage is ossified, and the diaphysis grows in length. The epiphyseal plate is composed of four zones  Growth in length continued 1. reserve zone (resting): is the region closest to the epiphyseal end and contains hyaline cartilage. 2. proliferative zone: next layer toward the diaphysis and stack like contains stacks of slightly larger chondrocytes. cons 3. Hypertrophy zone: contains chondrocytes that are larger than those in the proliferative zone. start swelling + you see spaces 4. zone of calcification/resorption: the zone closest to the diaphysis becomes calcified. and take away calcification The bone increases in length as long as the rate of cartilage production equals the rate by which it is replaced by bone. reserve lacunae associated w/ chondrocytes Osteoclasts ↳ take away anything thats calcified  Increasing the Diameter of the Developing Bbone does not use growth plate Bones increase in diameter; growth in diameter can continue even after longitudinal growth ceases. The diameter of bone increases by appositional playing down growth. on outside bone on bone Osteoblasts in the cellular layer of the periosteum add success layers of bone called circumferential lamellae. like outside layer of peeling At the same time, osteoclasts on the interior surface Onion I resorb bone and widen the marrow cavity. outside avoid medullary The final result is an increase in both the diameter and + getting cavity marrow cavity of the bone glow wall too thick or thin  Summary of Endochondral Bone Formation 1. Mesenchymal cells differentiate into chondroblasts (6-8 weeks). 2. The cartilage model of the future bony skeleton and the perichondrium form. Perichondrium is vascularized Cartilage model grows by interstitial and appositional grow 3. A bony collar is formed and cells in center of diaphysis hypertrophy (around 3rd month) 4. Cartilage in center calcifies and chondrocytes die leaving cavities within cartilage resulting in the primary center of ossification. 5. Periosteal buds penetrate cavity. Blood vessels invade carrying osteogenic cells with them, many of which will become osteoblasts and osteoclasts. Osteoclast eat away calcified cartilage enlarging spaces eventually combine to become the medullary cavity. 5. Cartilage continues to grow at ends of the bone. 6. Secondary ossification centers develop around time of birth 7. Cartilage remains at (1) epiphyseal (growth) plate and at (2) joint surface as articular cartilage  Bones Formed By Endochondral Formation All of the bones of the body are formed through endochondral ossification, except for the: flat bones of the skull, do not J use use mandible, and Intramembranous cartilage bone clavicles as model formation.  Intramembranous Ossification mesenchymal cells in the embryonic differentiate becomeasked skeleton gather together and begin to into osteoblast differentiate into osteogenic cells and then osteoblasts. early osteoblasts appear in a cluster makes bone called an ossification center. it osteoblasts secrete osteoid, organicprology a matrix (collagen and ground substance) , organize into which calcifies within a few days as plate like structure called crystals of calcium and phosphate are spongyboeent bone deposited on it  Intramembranous Ossification the entrapped osteoblasts become osteocytes completely surrounded osteogenic cells in the surrounding connective by bone tissue differentiate into new osteoblasts. becomes calcifed osteoid secreted around the capillaries results in a trabecular matrix osteoblasts on the surface of the spongy bone become the periosteum The periosteum then creates a protective layer of compact bone superficial to the trabecular bone.  Dilploe Flat bones, like those of the cranium, consist of a layer of diploë (spongy bone), lined on either side by a layer of compact bone The two layers of compact bone and makes the interior spongy bone work It stronger together to protect the internal organs. If the outer layer of a cranial bone fractures, the brain is still protected by the intact inner layer.  Summary of Intramembranous - do not need cartilage Intramembranous ossification follows steps. 1. Mesenchyme cells differentiate into a cluster of osteoblasts within a connective tissue and forms an ossification center 2. Clusters of osteoblasts form osteoid that becomes mineralized (form trabeculae) 3. Trabeculae radiate out from the ossification centers to join with neighboring trabeculae 4. A periosteum forms 5. Trabeculae deep to periosteum thicken, becoming compact lamellar bone (the rest stays trabecular-spongy bone- diploë)  Bone Tissue Functions supports the body facilitates movement protects internal organs produces blood cells (from bone marrow stores and releases minerals and fat  Bone Marrow There are two types of bone marrow: red and yellow. Red bone marrow is active containing blood stem cells that eel can become red blood cells, white blood cells, or platelets. differen It is essential for the body to function correctly Yellow bone marrow is made mostly of fat and is relatively medullary cavity - Primarily yellow inactive accumulation of fat  Bone Marrow (Continued) At birth, all bone marrow is red With age, more and more of it is converted to the yellow type (half of it is converted to yellow marrow by age seven) During emergencies the body converts yellow bone marrow to red Red marrow is found mainly in the bones such as hip bone, breast bone, skull, ribs, vertebrae and shoulder blades, and in the cancellous ("spongy") material at the proximal ends of the long bones Yellow bone marrow is located in the hollow cavity of long bones  Joints/Articulation There are two ways to categorize joints. 1. The first is by joint function. 2. The second way to categorize joints is by structure and the material that holds the bones of the joints together  Joint Function synarthroses Immovable joints skull sutures, the articulations between the teeth and the mandible, and the joint found between the first pair of ribs and the sternum. amphiarthroses slight movement distal joint between the tibia and the fibula and the pubic symphyisis of the pelvic girdle. diarthroses full movement elbow, shoulder, and ankle. Joint Structure 1. Fibrous Joints 2. Cartilagenous Joints 3. Synovial Joints  Fibrous Joints Fibrous Joints. Between the articulations of fibrous joints is thick connective tissue, and most fibrous joints are immovable (synarthroses). between two bones most are synarthrotic Types of fibrous joints: (1) Sutures are nonmoving joints (synarthroses) that connect bones of the skull. These joints have serrated edges that lock together with fibers of connective tissue. (2) A syndesmosis is a joint in which a ligament connects two bones, allowing for a little movement (amphiarthroses). The distal joint between the tibia and fibula is an example of a syndesmosis.  & areason Sutures and Fontanelles able / sutures come together typically Sutures allow the bones to move during the birth process. They act like an expansion joint. This allows the bone to enlarge evenly as the brain grows and the skull expands. During infancy and childhood, the sutures are flexible. Fontanels are the fibrous, membrane-covered gaps created when more than two cranial 'soft bones are juxtaposed. important in birth t brain growth  Fontanelles Anterior fontanelle (also called soft spot). know for exam wholes * This is the junction where the 2 frontal and 2 parietal bones meet. btwn Coronal + sagittal suture The anterior fontanelle closes between 9 months to 18 months second to close Posterior fontanelle. This is the junction of the 2 parietal bones and the occipital bone. btwn lamboidal + sagittal suture The posterior fontanelle usually closes first, before the anterior fontanelle, during the first several months of an infant's life.  Cartilagenous Joints that unite bones with cartilage There are two types of cartilaginous joints: 1. A synchrondosis is an immovable cartilaginous joint. -growthe joint between the first pair of ribs and the sternum. 2. A symphysis consists of a fibrocartilaginous pad that connects little bit of movement two bones. joint allows for some movement. hip bones connected by the pubic symphysis vertebrae connected by intervertebral discs Synchondrosis mo a Symphysis  Intervertebral disc The intervertebral disc is important in the normal functioning of the spine. It is a cushion of fibrocartilage and the principal joint between two vertebrae in the spinal column. outer portion made of fiblocartilage The intervertebral disc is made up of Annulus fibrosis Nucleus pulposus