Principles of Bones 2024 PDF

Principles of Bones Dr.Radi Al Saffar Dr. Shajiya S. Moosa ([email protected] ) Department of Anatomy  Learning Objectives After participating in this session and related activities, you should be able to:  Describe the macroscopic structure of bone  Underst...

Principles of Bones Dr.Radi Al Saffar Dr. Shajiya S. Moosa ([email protected] ) Department of Anatomy  Learning Objectives After participating in this session and related activities, you should be able to:  Describe the macroscopic structure of bone  Understand the functions of bone  Classify bones  Understand the process of ossification  Describe the neurovascular supply of bones  Define and classify cartilage  Understand common clinical conditions related to bones 2 Principles of Bones  Topics  Skeletal system  Structure of bone  Periosteum & bone marrow  Bone types & bony features  Cartilage  Development of bone  Neurovascular supply of a bone 3 Principles of Bones  The Skeletal System is made up of: 1. Bones & Joined 2. Cartilages together by Joints 4 Principles of Bones  Bones in the Skeletal System Head 22 Thorax 25 Vertebral column 33 Upper limbs 64 Lower limbs 62 Total 206 bones 5 Principles of Bones  Parts of the Skeleton Axial Appendicular Bones in the Bones of the midline & limbs bones of the (including the trunk girdles) Green: Axial skeleton Pink: Appendicular skeleton 6 Principles of Bones  Protection Movement Support Functions of Bones Storage of minerals Production of blood cells 7 Principles of Bones  Structure of Bone  Bone is a special type of connective tissue that has a calcified matrix.  It consists of: 1. Cells – osteoblast & osteoclast 2. Fibers - collagen Extracellular matrix 3. Mineralized ground substance 8 Principles of Bones rubbery shatters 9 Principles of Bones Structure of Bone Compact Cancellous Appears Appears as as a solid a branching mass network of trabeculae 10 Principles of Bones  General features of long bones  External &internal connective tissue covering  Periosteum.  Endosteum.  Tendinous & ligamentous attachment- sharpy fibers  Surface specialization for articulation - articular cartilage.  Bone marrow,  Blood vessels & nerves. Medullary Cavity  A long bone is characterised by a shaft between its proximal and distal ends  The shaft has a central medullary (L: ‘marrow’) cavity  Trabeculae are absent in the medullary cavity of a long bone  The shaft (particularly midway along it) has a thick shell of compact bone where its perimeter is subject to considerable forces  The medullary cavity of a long bone has a fibrous tissue lining, termed the endosteum (G. ‘within bone’).  Periosteum  Is the dense fibro cellular tissue which covers the external surface of bone except the articular surface.  It has an outer fibrous and inner cellular osteogenic layer.  Periosteum is highly vascular and richly supplied by nerves and is very sensitive.  Periosteum (outer layer) is well united at sites where muscles, tendons, and ligaments are attached to bone.  Bundles of collagen fibers known as Sharpy's fibers extend from the periosteum into the underlying bone. Endosteum  A layer of attenuated connective tissue with Osteogenic cells called Endosteum line the marrow cavity and the cavities of spongy bones.  Both the external and internal surfaces of bones are covered by layers of bone forming cells.  Bone Marrow  Bone marrow fills the spaces of spongy bones and the medullary cavity of long bones.  Red bone marrow is a prime site of blood cell production (for haemopoiesis), which consists of haemopoietic tissue embedded in adipose tissue.  Yellow bone marrow is almost entirely fat retains the capacity to revert to red marrow, particularly after severe blood loss In early life bone marrow throughout the body is red. Red marrow remains in the axial skeleton for life, but in the limbs becomes yellow marrow during adolescence. 14 Principles of Bones  Classification of bone based on shape Short bones Irregular bones Pneumatic bones e.g. carpal bones e.g. vertebra e.g. Paranasal air sinuses and Mastoid air cells Accessory bones Long bones e.g. humerus Sesamoid bones Flat bones Illu long bone.jpg eg.; Patella e.g. cranial bones ‫اﻟﺼﻮرة ﻟﺮؤ ﺘﻬﺎ ﺎﻟﺤﺠﻢ اﻟﻄﺒ‬ ‫اﺿﻐﻂ ﻋ‬  Bony Parts & Features  Ends & shaft (of long bones)  Flattened surfaces separated by borders  Bony features: e.g. elevations from traction on periosteum  Bone markings: e.g. grooves from tendons, nerves, vessels 16 Principles of Bones  Markings may be classified : elevations, facets, depressions and holes.  An elevation may be a line, a crest, a spine, a process, a condyle , a tubercle, a tuberosity or a trochanter.  A facet is a smooth, flat area.  A depression may be a fossa , a fovea , a groove or sulcus or a notch.  A hole may be a foramen , a fissure, a meatus, a canal or a hiatus.  Relations  Nerves & vessels directly related to bone may leave grooves or impressions  Structures directly related to bone (including underlying viscera) are endangered in fractures Principles of Bones 18  Articular surfaces  Articular (L. ‘joint’) surfaces are the areas of bone that articulate at synovial joints  Articular surfaces are the only external surfaces of a bone not surrounded by Posterior view of the knee joint periosteum.  Articular surfaces are covered by hyaline articular cartilage. Cartilage 20 Principles of Bones  Cartilage Types Hyaline Elastic Fibrocartilage cartilage cartilage orthopaedics glossary 21 Principles of Bones  Bone Development (by process of ossification)  Intramembranous for flat bones of skull  Endochondral for all other bones –primary center (appears in 6th- 8th week of embryo) –secondary centers (appear after birth) Primary centers in a 12-week-fetus 22 Principles of Bones Bone development is termed ossification.  The vast majority of bones develop from a hyaline cartilage precursor, by intracartilaginous (endochondral) ossification where a cartilage model is progressively replaced by bone.  Some bones develop from a fibrous tissue precursor, by intramembranous ossification.  These bones include the flat bones of the skull as well as parts of the clavicle and mandible.  24 Principles of Bones Primary center of ossification  A primary center of ossification appears in the center of the diaphysis(6th week of intrauterine life.)  Cartilage is progressively replaced by bone(at about 8th week) towards the epiphyses.  By birth majority of primary centres appear (except for the short bones in the hand and most of those in the foot). 25 Principles of Bones  Secondary centers of ossification  Secondary centres of ossification are growth centres typically located in the ends of the cartilage model for long bones. 26 Principles of Bones  Parts of developing long bones  Epiphysis: at ends of a long bone  Diaphysis: becomes the shaft of a long bone  Metaphysis: part of a diaphysis adjacent to the epiphyseal plate 27 Principles of Bones  Epiphyseal (growth) plate  A plate of hyaline cartilage responsible for growth in length.  Growth in length occurs at the metaphyseal surface of an epiphysial plate 28 Principles of Bones Duration of an epiphysis  The earlier an epiphysis appears, the later it fuses.  Epiphyses for larger long bones tend to appear before (and fuse after) those for smaller long bones. 29 Principles of Bones Appearance & fusion of epiphysis  Almost all secondary centres appear after birth (females generally at an earlier age than males)  Epiphyseal fusion occurs after puberty (females generally at an earlier age than males) 30 Principles of Bones  Growth of a long bone  Growth in width is from the periosteum  More growth in length occurs at one end (nutrient foramen is directed away from the growing end) 31 Principles of Bones Remodeling of a long bone Osteoclasts resorb (break down) old bone. 32 Principles of Bones  clinical How to distinguish epiphyseal plates from application fracture lines? On radiographs, epiphyseal plates undergoing fusion resemble fracture lines  Knowing the likely sites for epiphyses helps in avoiding mistakenly diagnosing a fracture  an epiphyseal plate may also be differentiated from a fracture by comparing with an x-ray of the corresponding bone on the other side of the body 33 Principles of Bones clinical application Determination of Skeletal Age Since epiphyses fuse in an ordered sequence, they can assist in determining the age of an individual from radiographic images or forensic skeletal examination. 34 Principles of Bones clinical application Impaired growth from epiphysial damage  In children & adolescents, an injury to an epiphysis or a fracture extending through the epiphyseal plate will impair subsequent growth  Bone infections spread from the blood stream tend to occur at the metaphysis (a site of vulnerable blood supply)  Interruption of blood supply to the epiphysis or metaphysis will similarly tend to impair normal growth 35 Principles of Bones  Supply To Bone And Cartilage  Bone tissue has a sensory nerve supply and a rich blood supply.  The periosteum also possesses vessels and abundant sensory nerve (particularly pain) fibres.  In a developing bone the entire cartilage model (including articular cartilage and the growth plate) is avascular and aneural except after conversion to bone at centres of ossification.  Cartilage that is not articular (e.g. of nasal septum) receives its only nutrition from perichondrial vessels. Blood supply of the long bones The blood supply of long bone is by 1. The main nutrient artery :-bone marrow and spongy bone. 2. The Periosteum arteries:-cortex of bones 3. The metaphyseal arteries are end arteries. 4. The epiphyseal :-epiphyses. During development the epiphyseal and metaphyseal arteries are ‘end arteries’ (i.e. do not link with each other) Upon closure of the growth plate the arteries anastomose The direction of blood flow is said to be largely centrifugal, i.e. from the branches of the nutrient artery outwards periosteum, to anastomose with the periosteal vessels. The short, flat and irregular bones are supplied by periosteal arteries (mainly) and the nutrient artery. Nutrient arteries may enter the bone at various points. Sites of vascular foramina 38 Principles of Bones clinical application Arteries supplying the shaft of a long bone Extensive stripping of the periosteum (e.g. during surgery) may directly deprive the underlying compact bone from its blood supply 39 Principles of Bones clinical application Arteries supplying the end of a long bone Interruption of blood supply from metaphyseal or epiphysial arteries endangers the bone and may impair growth 40 Principles of Bones  Fractures clinical application  A broken bone is termed a fracture (L. ‘break’).  If fractured bone is exposed to the air (by laceration of overlying skin) it is termed a ‘compound’ (open) fracture and has a significant risk of bone infection.  Adults tend to have stronger bones than ligaments, while children have the reverse 41 Principles of Bones  clinical application Fracture Healing  Healing of fractures is more rapid in children than in adults  Weight bearing bones heal slower than non- weight bearing bones 42 Principles of Bones  References Textbook: Eizenberg General Anatomy: Principles and Applications SECTION II: BODY SYSTEMS AND ORGAN STRUCTURE Chapter 4: Skeletal System and Bones Page no: 19 to 28 Thank You Thank you 45 Principles of Bones