Skeletal System Lecture PDF

Chapter 5: The Skeletal System Skeletal System Broken into 2 main parts: axial skeleton and appendicular skeleton Axial skeleton is made up of the bones that from the longitudinal axis of the body Appendicular skeleton is made up of the limbs and girdles that are attached to the...

Chapter 5: The Skeletal System Skeletal System Broken into 2 main parts: axial skeleton and appendicular skeleton Axial skeleton is made up of the bones that from the longitudinal axis of the body Appendicular skeleton is made up of the limbs and girdles that are attached to the Axial skeleton On the following slide, the axial skeleton is colored in blue Bony Functions Bones serve a variety of functions in the body. These include: Support Protection Movement Storage Blood Cell formation Bony Function Support The skeletal system forms the framework that supports the body It also functions to cradle the soft organs The bones of the leg serve as pillars when in standing and the thoracic rib cage supports the thoracic wall Bony Function Protection Bones will also protect soft organs These can be seen in several areas of the body including the rib cage and skull The ribs will protect the heart and lungs, while the skull will protect the brain Bony Function Movement Bones serve as an attachment for muscles It is when these muscles contract, the movement occurs Any motion completed results in a bone being moved Bony Function Storage Bones are a storage site for both calcium and phosphorus Fat is also stored in the bone marrow Hormones control the movement of calcium to and from the bones Bony Function Blood Cell Formation Blood cells will form in the marrow cavities of some bones This process is called hematopoiesis Classifications of Bones The adult skeleton is compromised of 206 bones There are two main types of bones: Compact and Spongy Compact bone is homogeneous in nature and appears dense and smooth Spongy bone is composed of needlelike pieces of bone and open spaces Bones are also grouped according to shape Long – longer than wide, compact in nature, make up limbs Short – cubed shaped, spongy, good example is the patella Flat – thin and flat, spongy bone between 2 layers of compact, ie.) sternum Structure of Bone For the sake of this lecture, we will be focusing on the structure of a long bone The shaft of the long bone is called the diaphysis, this will make up the majority of the bone’s length It is covered by a layer of connective tissue called the periosteum Sharpey’s fibers are the connective tissue fibers that attach the periosteum to the bone. Structure of Bone At either end is a epiphysis, this is a thin layer of compact bone with an area of spongy bone at the center The periosteum will end prior to the epiphysis, instead, a layer of articular cartilage will cover the epiphysis As previous discussed, this is made up a hyaline cartilage, which provides a smooth surface for joint surfaces A thin line can also be noted in an adult long bone, this is called the epiphyseal line This line is a remnant of the epiphyseal plate, which is responsible for length growth during childhood. Structure of Bone The inner shaft is covered by the endosteum The center cavity of the bone is called the medullary cavity, which serves as a fat storage (yellow marrow) site in adults In infants, the medullary cavity forms red blood cells (red marrow) In adults, red marrow is found in spongy bone in flat bones and the epiphysis of some long bones Microscopic Anatomy of Bone Bones are not smooth, completely dense structures as previously thought They have a variety of passages for nerves and vessels Osteocytes are mature bone cells found within the matrix in small cavities call lacunae The lacunae are arranged in circles around a central canal called a Haversian canal Each complex consisting of a central canal and matrix is called an osteon, or Haversian system Microscopic Anatomy of Bone These central canals will travel the length of the long bone There are also small canals called canaliculi, that will radiate outward from the central canal These canaliculi provide a nutrient system for the entire bone The nutrient system is completed by perforating canals (Volkmann’s Canals) These canals serve as a link between the hard outside of the bone and the inside, they will run at right angles to the shaft Bone Growth As previously discussed, the skeleton is made up of bone and connective tissue, two of the strongest substances in the body In an embryo, the skeleton is made up of hyaline cartilage, this will change as the child grows and the skeleton will be replace by bone Only a small area will have cartilage remain into adulthood ie.) bridge of nose, parts of ribs and the joints Bone Growth The growth process will use the hyaline cartilage as a map to form the bone, this process is called ossification Ossification involves two main phases The first phase is where the hyaline cartilage is totally covered by a bone matrix made up of cells called osteoblasts Slowly, the cartilage is absorbed, leaving a cavity for new bone to form After birth, the only remaining cartilage is found in the articular cartilage and epiphyseal plate The cartilage is continuously regrown with old cartilage being replaced by bone Bone Growth Bones must also widen as well as lengthen This is done simply by osteoblastic activity in the periosteum adding new bone to the face of the diaphysis This process is primarily controlled by hormones and is completed during adolescence when the epiphyseal plates are fully replaced by bone Bone Remodeling Bone is a dynamic system that is always changing based on the environment The main two factors affecting bone is the calcium level in the blood, and the pull of gravity and muscles on the skeleton When the body senses a decrease in blood calcium, the parathyroid gland is stimulated to release PTH hormone This activates osteoclasts, which are bone destroying cells, that will break down the bone matrix and release calcium into the blood If too much calcium is noted (hypercalcemia), excess calcium is stored in the bone matrix as hard calcium salts Bone Remodeling The second factor is also essential as the body needs to retain normal growth proportions and strength during development Muscle size and strength must also be accounted for with larger and thicker projections for the muscles to attach to At these sites, osteoblasts are attached and become osteoclasts Bones of bedridden people will also reflect these changes as their bones will loose density and mass secondary to disuse Bone Remodeling Bone integrity is also influenced by external forces If the force exceeds the bones strength, a fracture occurs Fractures are classified a variety of ways The initial way is either open or closed A close fracture is one that is still contained within the skin An open fracture is one where the broke bone penetrates the skin Fractures are treated by reduction, or alignment of the bone ends Bone Remodeling Even though the bone is realigned by the surgeon, the body must heal itself This is achieved through 4 phases: Hematoma formation Fibrocartilage callus forms Bony Callus forms Bone Remodeling occurs Hematoma Formation Blood vessels are ruptured when a bone is broken When this happens, a blood filled swelling is formed This is called a hematoma Bone cells that are deprived of nutrition will eventually die Fibrocartilage Callus Forms Granulation tissues begin to form, think of this as growth of new capillaries This occurs in the hematoma at the site of damage, while at the same time disposal of dead tissue by phagocytes As this is occurring, a mass of repair tissue containing cartilage matrix, bony matrix and collagen is also formed to act as a splint and hold the ends of the bones together Bony Callus Forms As more osteoblasts and osteoclasts populate the area, the fibrocartilage callus is slowly replaced The bony callus is formed primarily of spongy bone Bone Remodeling Occurs Over the next weeks to months, the bony callus is remodeled in response to mechanical stresses placed on it This will continue to occur until it forms a strong, permanent patch at the fracture site Axial Skeleton Forms the longitudinal axis of the body Divided into three parts 1. Skull 2. Vertebral column 3. Bony thorax  Cranium Skull Facial bones Clavicle Thoracic cage Scapula (ribs and Sternum sternum) Rib Humerus Vertebra Vertebra Radius l Ulna Sacru column m Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (a) Anterior view Cranium Bones of pectoral Clavicle girdle Scapula Sternum Upper Rib limb Humerus Vertebr R a adius Bones of Ulna pelvic Carpals girdle Phalanges Metacarpals Femur Lower Tibia limb Fibula (b) Posterior view Skull Two sets of bones form the skull 1. Cranium bones enclose the brain 2. Facial bones Hold eyes in anterior position Allow facial muscles to express feelings Bones are joined by sutures Only the mandible is attached by a freely movable joint Skull 8 cranial bones protect the brain 1 Frontal bone 2 Occipital bone 3 Ethmoid bone 4 Sphenoid bone 5, 6 Parietal bones (pair) 7, 8 Temporal bones (pair) Skull 14 facial bones 1, 2 Maxillae (pair) 3, 4 Palatine bones (pair) 5, 6 Lacrimal bones (pair) 7, 8 Zygomatic bones (pair) 9, 10 Nasal bones (pair) 11 Vomer bone 12, 13 Inferior nasal conchae (pair) 14 Mandible Coronal suture Frontal bone Parietal bone Sphenoid bone Temporal bone Ethmoid bone Lambdoid Lacrimal bone suture Squamous suture Nasal bone Occipital bone Zygomatic process Zygomatic bone Maxilla External acoustic meatus Mastoid process Alveolar processes Styloid process Mandible (body) Mental foramen Mandibular ramus  Frontal bone Cribriform plate Ethmoid Crista galli bone Sphenoid bone Optic canal Sella turcica Foramen ovale Temporal bone Jugular foramen Internal acoustic meatus Parietal bone Occipital bone Foramen magnum  Maxilla Hard (palatine process) Incisive fossa palate Palatine bone Maxilla Zygomatic bone Sphenoid bone Temporal bone (greater wing) (zygomatic process) Foramen ovale Vomer Mandibular fossa Carotid canal Styloid process Mastoid process Jugular foramen Temporal bone Occipital condyle Parietal bone Foramen magnum Occipital bone Coronal suture Frontal bone Parietal bone Nasal bone Superior orbital fissure Sphenoid bone Optic canal Ethmoid bone Temporal bone Lacrimal bone Zygomatic bone Infraorbital Middle nasal concha foramen of ethmoid bone Maxilla Inferior nasal concha Vomer Mandible Alveolar processes Mental foramen Sagittal suture Anterior view Parietal bone Lambdoid suture Occipital bone Mastoid process of temporal bone Posterior view Skull Paranasal sinuses Hollow portions of bones surrounding the nasal cavity Functions of paranasal sinuses Lighten the skull Amplify sounds made as we speak Figure 5.13a Paranasal sinuses. Frontal sinus Ethmoid sinus Sphenoidal sinus Maxillary sinus (a) Anterior view Figure 5.13b Paranasal sinuses. Frontal sinus Ethmoid sinus Sphenoid al sinus Maxillary sinus (b) Medial view Skull Hyoid bone Closely related to mandible and temporal bones The only bone that does not articulate with another bone Serves as a movable base for the tongue Aids in swallowing and speech Figure 5.14 Anatomical location and structure of the hyoid bone. Greater horn Lesser horn Body Vertebral Column (Spine) Vertebral column provides axial support Extends from skull to the pelvis 26 vertebral bones are separated by intervertebral discs 7 cervical vertebrae are in the neck 12 thoracic vertebrae are in the chest region 5 lumbar vertebrae are associated with the lower back Sacrum (formed by fusion of 5 vertebrae) Coccyx (formed by fusion of 3–5 vertebrae) Anterior Posterior 1st cervical vertebra Cervical curvature (atlas) 2nd cervical (concave) 7 vertebrae, vertebra C1 – C 7 (axis) 1st thoracic vertebra Transverse process Spinous Thoracic curvature process (convex) 12 vertebrae, Intervertebral T1 – T12 disc Intervertebral foramen 1st lumbar vertebra Lumbar curvature (concave) 5 vertebrae, L1 – L5 Sacral curvature (convex) 5 fused vertebrae Coccyx 4 fused vertebrae Vertebral Column (Spine) Primary curvatures Spinal curvatures of the thoracic and sacral regions Present from birth Form a C-shaped curvature in newborns Secondary curvatures Spinal curvatures of the cervical and lumbar regions Develop after birth Form an S-shaped curvature in adults Vertebral Column (Spine) Parts of a typical vertebra Body (centrum) Vertebral arch Pedicle Lamina Vertebral foramen Transverse processes Spinous process Superior and inferior articular processes  Posterior Lamina Vertebral Figure 5.17 A typical vertebra, superior view. arch Transverse Spinous process process Superior articular process and facet Pedicle Vertebral foramen Body Anterior. (a) ATLAS AND AXIS Transverse Posterior process arch Anterior arch Superior view of atlas (C1) Spinous Transverse process process Facet on superior articular process Dens Body Superior view of axis (C2)  (b) TYPICAL CERVICAL VERTEBRAE Facet on superior Spinous articular process process Vertebral foramen Transverse Transverse process foramen Superior view Superior articular Body process Spinous process Transverse process Facet on inferior articular process Right lateral view.  (c) THORACIC VERTEBRAE Spinous process Transverse Vertebral process foramen Facet Facet on for rib superior articular process Body Superior view Facet on Body superior articular process Facet on transverse process Costal facet Spinous for rib process Right lateral view. (d) LUMBAR VERTEBRAE Spinous process Vertebral foramen Transverse process Facet on superior Body articular process Superior view Superior Body articular process Spinous Facet on inferior process articular process Right lateral view  SuperiorAuricular Ala Sacral articularsurface canal process Body Median Sacrum sacral crest Posterior sacral foramina Sacral Coccyx hiatus. Thoracic Cage Bony thorax, or thoracic cage, protects organs of the thoracic cavity Consists of three parts 1. Sternum 2. Ribs True ribs (pairs 1–7) False ribs (pairs 8–12) Floating ribs (pairs 11–12) 3. Thoracic vertebrae  T1 vertebra Jugular notch Clavicular notch Manubrium Sternal angle Body Xiphisternal Sternum True joint ribs Xiphoid (1–7) process False ribs (8–12) Intercostal spaces L1 Floating vertebra Costal cartilage ribs (11, 12) (a) Appendicular Skeleton Composed of 126 bones Limbs (appendages) Pectoral girdle Pelvic girdle © 2018 Pearson Education, Inc.  Cranium Skull Facial bones Clavicle Thoracic cage Scapula (ribs and Sternum sternum) Rib Humerus Vertebra Vertebra Radius l Ulna Sacru column m Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (a) Anterior view Cranium Bones of pectoral Clavicle girdle Scapula Sternum Upper Rib limb Humerus Vertebr R a adius Bones of Ulna pelvic Carpals girdle Phalanges Metacarpals Femur Lower Tibia limb Fibula (b) Posterior view Bones of the Shoulder Girdle Also called pectoral girdle Composed of two bones that attach the upper limb to the axial skeletal 1. Clavicle 2. Scapula Light, poorly reinforced girdle Allows the upper limb a exceptional flexibility Figure 5.21a Bones of the shoulder girdle. Acromio- clavicular Clavicle joint Scapula (a) Articulated right shoulder (pectoral) girdle showing the relationship to bones of the thorax and sternum Figure 5.21b Bones of the shoulder girdle. Posterior Sternal (medial) end Acromial Anterior (lateral) end Superior view Acromial end Sternal end Anterior Posterior Inferior view (b) Right clavicle, superior and inferior views  Coracoid process Suprascapular notch Figure 5.21c Bones of the shoulder girdle. Superior Acromion angle Glenoid cavity at lateral angle Spine Medial border Lateral border (c) Right scapula, posterior aspect  Acromion Figure 5.21d Bones of the shoulder girdle. Suprascapular notch Superior border Coracoid process Superior angle Glenoid cavity Lateral angle Lateral (axillary) Medial border (vertebral) border Inferior angle (d) Right scapula, anterior aspect Bones of the Upper Limbs Humerus Forms the arm Single bone Proximal end articulation Head articulates with the glenoid cavity of the scapula Distal end articulation Trochlea and capitulum articulate with the bones of the forearm  Greater Head of tubercle humerus Lesser Figure 5.22a Bones of the right arm and forearm. tubercle Anatomical neck Intertubercular sulcus Deltoid tuberosity Radial fossa Medial epicondyle Coronoid fossa Capitulum Trochlea (a)  Head of humerus Figure 5.22b Bones of the right arm and forearm. Anatomical neck Surgical neck Radial groove Deltoid tuberosity Medial epicondyle Olecranon fossa Lateral Trochlea epicondyle (b) Bones of the Upper Limbs The forearm has two bones 1. Ulna—medial bone in anatomical position Proximal end articulation Coronoid process and olecranon articulate with the humerus 2. Radius—lateral bone in anatomical position Proximal end articulation Head articulates with the capitulum of the humerus  Trochlear notch Olecranon Head Figure 5.22c Bones of the right arm and forearm. Coronoid process Neck Radial Proximal tuberosity radioulnar joint Radius Ulna Inter- osseous membrane Ulnar Radial Distal styloid styloid process process radioulnar joint (c) Bones of the Upper Limbs Hand Carpals—wrist bones 8 bones arranged in two rows of 4 bones in each hand Metacarpals—palm bones 5 per hand Phalanges—fingers and thumb 14 phalanges in each hand In each finger, there are 3 bones In the thumb, there are only 2 bones Figure 5.23 Bones of the right hand, anterior view. Distal Middle Phalanges (fingers) Proximal 4 3 2 Metacarpals 5 (palm) 1 Hamate Trapezium Carpals Pisiform Trapezoid (wrist) Triquetrum Scaphoid Lunate Capitate Ulna Radius Bones of the Pelvic Girdle Formed by two coxal (ossa coxae) bones Composed of three pairs of fused bones 1. Ilium 2. Ischium 3. Pubis Pelvic girdle = two coxal bones, sacrum Pelvis = two coxal bones, sacrum, coccyx Bones of the Pelvic Girdle The total weight of the upper body rests on the pelvis Pelvis protects several organs Reproductive organs Urinary bladder Part of the large intestine Figure 5.24a The bony pelvis. Iliac crest Sacroiliac joint llium Coxal bone Sacrum (or hip bone) Pelvic brim Pubis Coccyx Ischial spine Acetabulum Ischium Pubic symphysis Pubic arch (a)  Ilium Figure 5.24b The bony pelvis. Ala Iliac crest Posterior superior iIiac Anterior superior spine iliac spine Posterior inferior Anterior inferior iIiac spine iliac spine Greater sciatic notch Acetabulum Ischial body Body of pubis Ischial spine Pubis Ischial tuberosity Inferior pubic ramus Ischium Obturator Ischial ramus foramen (b) Bones of the Pelvic Girdle The female’s pelvis Inlet is larger and more circular Shallower, on the whole, and the bones are lighter and thinner Ilia flare more laterally Sacrum is shorter and less curved Ischial spines are shorter and farther apart; thus, the outlet is larger Pubic arch is more rounded because the angle of the pubic arch is greater  False pelvis Figure 5.24c The bony pelvis. Inlet of true pelvis Pelvic brim Pubic arch (less than 90º) False pelvis Inlet of true pelvis Pelvic brim Pubic arch (more than 90º) (c) Bones of the Lower Limbs Femur—thigh bone The heaviest, strongest bone in the body Proximal end articulation Head articulates with the acetabulum of the coxal (hip) bone Distal end articulation Lateral and medial condyles articulate with the tibia in the lower leg  Surgical neck Head Figure 5.25a Bones of the right thigh and leg.Inter- trochanteric line Lesser trochanter Lateral epicondyle Medial epicondyle Patellar surface (a)  Greater Head trochanter Figure 5.25b Bones of the right thigh and leg. Inter- trochanteric Lesser trochanter crest Gluteal tuberosity Intercondylar fossa Medial Lateral condyle condyle (b) Bones of the Lower Limbs The lower leg has two bones 1. Tibia—shinbone; larger and medially oriented Proximal end articulation Medial and lateral condyles articulate with the femur to form the knee joint Distal end articulation Medial malleolus forms the inner part of the ankle 2. Fibula—thin and sticklike; lateral to the tibia Has no role in forming the knee joint Distal end articulation Lateral malleolus forms the outer part of the ankle  Intercondylar eminence Lateral Medial Figure 5.25c Bones of the right thigh and leg. condyle condyle Head Tibial tuberosity Proximal tibiofibular joint Interosseous membrane Anterior border Fibula Tibia Distal tibiofibular joint Medial Lateral malleolus malleolus (c) Bones of the Lower Limbs Foot Tarsals—7 bones Two largest tarsals are the: Calcaneus (heel bone) Talus Metatarsals—5 bones form the sole of the foot Phalanges—14 bones form the toes Figure 5.26 Bones of the right foot, superior view. Phalanges: Distal Middle Proximal Tarsals: Medial Metatarsals cuneiform Tarsals: Intermediate cuneiform Lateral cuneiform Navicular Cuboid Talus Calcaneus Bones of the Lower Limbs Arches of the feet Bones of the foot are arranged to form three strong arches Two longitudinal One transverse Figure 5.27 Arches of the foot. Medial longitudinal arch Transverse arch Lateral longitudinal arch