Skeletal_System

Page 2: Learning Objectives

• Name the classifications of bones by shape, and give an example of each.

• List and describe the components of a long bone (macroscopic)

• Describe the structure and function of spongy bone versus compact bone.

Page 3: Learning Objectives

• Describe the four types of cells in bone tissue and their function.

• List and discuss the general functions of bone tissue.

• Describe the two types of bone formation (intramembranous and endochondrial ossification)

Page 6: Organs of the skeletal system

• Organs of the skeletal system include:

  • Bones

  • Structures that connect bones to other structures e.g., ligaments, tendons, cartilages.

Page 7: Functions of the skeletal system

• Functions:

  • Support – structural framework

    • E.g., bones in legs and pelvis support the trunk

  • Protection of underlying organs

    • E.g., skull - brain, thorax (rib cage) - heart and lungs

  • Movement & anchorage of muscles

    • Skeletal muscles & tendons attach to bones.

    • Muscle pull on bones to move them.

    • Joints

Page 8: Additional functions of the skeletal system

• Functions:

  • Mineral Homeostasis

    • Bone stores minerals e.g., calcium, phosphorus

    • Released when needed

  • Haematopoiesis

    • All blood cells are formed in the red marrow of certain bones.

  • Energy reserve (triglycerides)

    • Yellow marrow (adipocytes) in the shaft of long bones

Page 10: Classification of Bones

• Bones classified according to shape:

  • Long bones - shaft with 2 knob-like ends.

    • E.g., thigh bone (femur) & upper arm bone (humerus).

  • Short bones - cube-like (roughly same l & w.

    • E.g., wrist bones (carpals), ankle bones (tarsals).

Page 11: Classification of Bones (continued)

• Flat bones – thin; provide extensive muscle attachment surfaces.

  • E.g., most skull bones, sternum (breast bone), scapulae (shoulder blades), ribs.

• Irregular bones – varied, complex shapes.

  • E.g., vertebrae, auditory ossicles.

• Sesamoid bones - develop within a tendon in areas of tension/friction/stress

  • E.g., the patella (kneecap).

Page 15: Bone Structure

• Macroscopic Anatomy of a typical long bone (e.g., humerus):

  1. Diaphysis - shaft.

  • Long cylinder of compact bone

  • central medullary cavity (filled with yellow marrow)

  2. Endosteum – single, inner lining of medullary cavity (dense irregular CT).

  3. Epiphyses (pl) - expanded proximal & distal ends

  • consist mainly of spongy bone (with red bone marrow)

Page 16: Bone Structure (continued)

• Articular cartilage - pad of hyaline cartilage on the epiphyses.

  • "shock absorber“ at joints

  • reduce friction

• Metaphysis – between diaphysis and epiphysis

• Periosteum - outer, fibrous, protective covering of diaphysis (Dense irregular CT)

  • rich supply of blood & lymph vessels, nerves (nutrition)

  • Responsible for growth in width

• Nutrient Foramen - canal allowing blood vessels to enter and leave bone.

• Epiphyseal plate - Hyaline cartilage at junction of diaphysis and epiphyses

  • Allows for growth in length

• Epiphyseal line - remnant of epiphyseal plate.

Page 19: Histology of Bone

• Chemical Composition of Bone

  • Organic components (35%):

    • Cells:

      • Osteogenic cells

        • derived from mesenchyme

        • Locations: inner periosteum, endosteum

        • Can undergo mitosis and become osteoblasts.

Page 20: Cells in Bone Tissue

• Osteoblasts

  • form bone matrix by secreting collagen

  • cannot undergo mitosis.

• Osteocytes

  • mature - derived from osteoblasts

  • cannot undergo mitosis

  • maintain daily cellular activities (i.e. exchange of nutrients & wastes with blood), repair

  • Star-shaped with numerous processes

Page 21: Cells in Bone Tissue (continued)

• Osteoclasts

  • Large cells; in endosteum

  • bone resorption (i.e. destruction of bone matrix)

  • development, growth, maintenance & repair of bone.

Page 23: Functions of Bone Cells

• Osteoblast cells produce the extracellular matrix – collagen fibers and other constituents.

• Osteocytes – these cells are involved in the day-to-day homeostasis of bone tissue including repair.

• Osteoclast cells cause resorption of bone tissue in response to hormones.

  • Calcium levels in the blood are held constant because of this ability by osteoclasts

Page 25: Histology of Bone (continued)

• Inorganic component (65%): Hydroxyapatite (mineral salts)

  • primarily calcium phosphate gives bone hardness/rigidity.

Page 26: Microscopic Structure of Compact Bone

• Bone tissue – typical CT with cells, matrix, fibers

• Compact Bone - solid, dense, smooth.

• Structural unit = Haversian System or Osteon.

  • elongated cylinders cemented together to form long axis of bone;

Page 32: Microscopic Structure of Spongy (Cancellous) Bone

• poorly organized trabeculae (small needle-like pieces of bone)

• lots of open space between them - lattice.

• Sometimes with red marrow

• No osteons

• Osteocytes lie in lacunae in trabecula – cannaliculi radiate from them

• nourished by diffusion from nearby Haversian canals.

Bone Formation (Osteogenesis/ossification)

• The "skeleton" of an embryo is composed of CT (formed from mesenchyme and hyaline cartilage), shaped like bones.

• This "skeleton" provides supporting structures for ossification to begin.

• At about 6-8 weeks of gestation, ossification begins and continues throughout adulthood.

Intramembranous Ossification

• Bone forms on or within a CT membrane.

• Examples include flat bones like skull bones and clavicles.

• Steps:

  • Development of ossification centre

    • Mesenchyme; osteogenic cells; osteoblasts

    • Osteoblasts begin to secrete matrix & eventually become surrounded by it

  • Calcification

    • Cells (now osteocytes) in lacunae

    • Minerals deposited

    • Matrix hardens

  • Trabeculae form

    • Small bone spicules from matrix built up into a network

    • Blood vessels grow into the spaces

    • CT forms red bone marrow

  • Periosteum develops

    • Mesenchyme at the periphery develops into the periosteum

    • Layer of compact bone develops below periosteum

Endochondral Ossification

• Bone is formed from a hyaline cartilage model.

• Most bones form in this manner.

• Steps:

  • Cartilage model develops

    • Mesenchyme gather in the shape of the bone to be formed and develop into chondroblasts

    • Chondroblasts secrete cartilage model (hyaline cartilage)

  • Growth of cartilage model

    • Cells (now chondrocytes) in matrix secrete more matrix

    • Cartilage model increases in length (by cell division)

    • Perichondrium surrounds the model

  • Primary ossification centre

    • Cells in perichondrium become osteoblasts that produce compact bone

    • Perichondrium changes to periosteum

    • Blood vessels grow into the spaces within the calcified matrix

    • Eventually form into spongy bone area called the primary ossification centre

  • Medullary cavity

    • Primary ossification centre expands

    • Osteoclasts break down some of the spongy bone in the cavity

    • Medullary cavity forms in the shaft

  • Secondary ossification centre

    • These develop in the epiphyses

    • However, no marrow is produced here

  • Articular cartilage

    • Hyaline cartilage produced that covers epiphyses

    • Hyaline cartilage between diaphysis and epiphysis (epiphyseal plate)

    • Responsible for lengthwise growth of bone

Bone Growth

• Continues into the third decade of life

• Hormones create differences in the growth rate of bones of different genders

• Growth in thickness

  • Bones grow in diameter by the combined action of osteoblasts & osteoclasts

  • Osteoclasts enlarge the diameter of the medullary cavity by eating away the bone of its walls

  • The osteoblasts from the periosteum build new bone around the outside of the bone

  • Combined action results in a bone with a larger diameter and larger medullary cavity - produced from a smaller bone with a smaller medullary cavity

Learning Objectives

• Distinguish between the axial and appendicular skeleton.

• Account for the bones located in the axial skeleton (skull, hyoid, auditory ossicles).

• List the 5 major curvatures of the vertebral column and identify the number of vertebrae in each.

• List the components of the thoracic cage.

• Distinguish between true, false, and floating ribs.

• Name the bones in the upper limbs & pectoral girdle.

• Name the bones in the lower limbs & pelvic girdle.

• Identify the major bone markings.

• List the major joints of the body and describe the structure and range of motion found in each.

Bones

• Bones have distinct markings:

  • Openings/foramina - holes that allow blood vessels and/or nerves & ligaments to pass through

  • Depressions: e.g., those involved in joint formation

    • Fossa, groove, fissure

  • Processes: projections for joints, attachment of ligaments & tendons, muscles

    • Fissure, foramen, fossa, sulcus, meatus, condyle, facet, head, crest, epicondyle, line, spinous process, trochanter, tubercle, tuberosity

The Skull

• The skull includes the cranium (brain case) and facial bones.

• All the bones of the skull (except the mandible) are interlocked along structures called sutures.

• Suture- area where skull bones fuse together (articulate).

• Function:

  • Enclose fluid-filled cranial cavity (cushion/support brain)

  • Blood vessels, nerves, membranes attach to inner cranial surface

  • Air-filled chambers (sinuses); lined with mucous membranes; produce mucous, lighten skull, resonating areas for sounds

Page 72:

• Cranium:

  • Frontal bone: forms the forehead, contains 2 frontal sinuses, forms the superior portion of the eye socket (orbit)

  • Paired Parietal bones: located behind the frontal bone, form the superior and lateral aspects of the cranium

  • Occipital bone: located at the posterior-inferior (base) of the cranium

Page 74:

• Frontal sinus

• Ethmoid sinuses

• Maxillary sinus

Page 75:

• Bones of the cranium:

  • Parietal bone

  • Frontal bone

  • Temporal bone

  • Nasal bone

  • Occipital bone

  • Maxilla

  • Zygomatic bone

  • Mandible

Page 76:

• Cranium:

  • Foramen magnum ("large hole") in the occipital bone allows nerve fibers to pass from the brain to the spinal cord

  • Occipital condyles: rounded processes on either side of the foramen magnum, articulate with the first vertebra (atlas)

Page 77:

• Sagittal suture

• Lambdoid suture

• Parietal bone suture

• External occipital protuberance

• Superior nuchal line

• Inferior nuchal line

• Mastoid process

• Zygomatic arch

• Occipital condyle

• Styloid process

• Lateral pterygoid plate

• Nasal septum

• Medial pterygoid plate

• Horizontal plate

• Pterygoid hamulus

• Hard palate

• Palatine process

Page 78:

• Cranium:

  • Paired Temporal bones: located inferior-lateral to the parietal bones, form the inferior aspects of the cranium

  • Internal: Ethmoid bone (between the eyes)

  • Sphenoid bone (skull; butterfly-shaped) connects with all other facial bones

Page 79:

• Sagittal suture

• FRONTAL BONE

• Coronal suture

• Frontal squama

• Supraorbital foramen

• PARIETAL BONE

• Supraorbital margin

• Squamous suture

• Optic foramen

• SPHENOID BONE

• Superior orbital fissure

• Orbit

• TEMPORAL BONE

• ETHMOID BONE

• NASAL BONE

• LACRIMAL BONE

• Inferior orbital fissure

• Infraorbital foramen

• Middle nasal concha

• ZYGOMATIC BONE

• Perpendicular plate

• MAXILLA

• INFERIOR NASAL CONCHA

• Alveolar process of maxilla

• VOMER

• MANDIBLE

• Mental foramen

Page 80:

• Zygomatic arch

• FRONTAL BONE

• Coronal suture

• SPHENOID BONE

• ZYGOMATIC BONE

• PARIETAL BONE

• ETHMOID BONE

• Temporal squama

• LACRIMAL BONE

• Squamous suture

• Lacrimal fossa

• NASAL BONE

• TEMPORAL BONE

• Temporal process

• Zygomatic process

• Infraorbital foramen

• Lambdoid suture

• MAXILLA

• Mastoid portion

• Mandibular fossa

• OCCIPITAL BONE

• External occipital protuberance

• External auditory meatus

• Mastoid process

• HYOID BONE

• Styloid process

• Foramen magnum

Page 81:

• Sagittal suture

• PARIETAL BONES

• OCCIPITAL BONE

• Lambdoid suture

• Sutural bones

• External occipital protuberance

• Superior nuchal line

• TEMPORAL BONE

• Inferior nuchal line

• Mastoid process

• Foramen magnum

• Occipital condyle

• Middle nasal concha

• Styloid process

• Hard palate

• Horizontal plate

• VOMER

• Palatine process

• MANDIBLE

• Posterior view

Page 82:

• The facial bones (14):

  • Shape the face

  • Attachment for various muscles that move the jaw and control facial expressions

  • Protect and support entrance of digestive and respiratory systems

Page 83:

• The facial bones (14):

  • 2 maxillae: mostly upper jaw

  • 1 mandible: lower jaw (movable)

  • 2 zygomatic bones: cheek prominence

Page 84:

• The facial bones (14):

  • 2 nasal bones: bridge of the nose

  • 1 vomer (part of nasal septum)

  • 2 inferior nasal conchae (inferior portions of the lateral nasal wall)

  • 2 Lacrimal bones: lateral and posterior to the nasal bones, inner walls of the eye socket

  • 2 Palatine bones: posterior portion of the hard palate, parts of nasal cavity & orbits

Page 85:

• Hyoid Bone:

  • Location: in the neck, between the lower jaw and larynx

  • Held in place by muscles and ligaments

  • Function: supports the tongue

• Ear: 6 bones

Page 87:

• Vertebral Column (26 bones):

  • Irregular bones

  • Divided into 5 curvatures:

    • Cervical curvature: 7 vertebrae in the neck, including the Atlas (nodding) and axis (turn head)

    • Thoracic curvature: 12 vertebrae in the thoracic cavity, articulate with ribs

    • Lumbar curvature: 5 vertebrae in the abdominal cavity

    • Sacrum: 5 fused vertebrae, posterior of the pelvis

    • Coccyx: 3-5 vertebrae of the tailbone

Page 90:

• Vertebral Column:

  • Intervertebral disk: protective pad of fibrocartilage between individual vertebrae, a slightly movable joint

Page 91:

• General Structure of Vertebrae:

  • Body (centrum): large, solid anterior region

  • Vertebral arch: posterior region

    • Pedicle: short bony posterior projection

    • Lamina: flattened plates that articulate posteriorly into the spinous process

  • Vertebral foramen: opening through which the spinal cord passes

  • Processes: attachment of muscles (spinous, transverse, articular)

Page 93:

• Intervertebral foramen

• Vertebral body

• Nucleus pulposus

• Annulus fibrosus

• Normal intervertebral disc

• Compressed intervertebral disc in a weight-bearing situation

Page 94:

• Thorax (Ribs and sternum):

  • Rib cage = ribs, sternum, thoracic vertebrae & costal cartilage

• Sternum (breastbone):

  • Manubrium: upper portion, resembles a handle, articulates with the clavicle

  • Body: middle vertical portion, site where most ribs articulate anteriorly

  • Xiphoid process: lower cartilaginous extension from the body

Page 95:

• Suprasternal notch

• Clavicular notch

• Manubrium

• Sternal body

• Angle

• Xiphoid process

• Anterior view of sternum

Note

Page 96:

• Ribs (12 pairs):

  • Articulate anteriorly with sternum; posteriorly with thoracic vertebrae

  • True ribs = 7 pairs that articulate directly with sternum (through costal (hyaline) cartilage)

  • False ribs – 3 pairs; articulate with 7th ribs

  • Floating ribs = 11th and 12th pair

    • These ribs do not articulate anteriorly.

Page 97:

• The appendicular skeleton (126) the bones of the upper and lower extremities

Page 98:

• SKULL

  • Cranial portion

  • Facial portion

• PECTORAL (SHOULDER) GIRDLE

  • Clavicle

  • Scapula

• THORAX

  • Sternum

  • Ribs

• UPPER LIMB

• VERTEBRAL COLUMN

• PELVIC (HIP) GIRDLE

  • Ulna

  • Radius

• GIRDLE

  • Carpals

  • Phalanges

  • Metacarpals

• LOWER LIMB (EXTREMITY)

  • Femur

  • Patella

  • Tibia

  • Fibula

  • Tarsals

  • Metatarsals

  • Phalanges

Page 99:

• The appendicular skeleton

  • The pectoral (shoulder) girdle (4 bones) connects the upper limbs to the rib cage

    • anterior clavicles (2) = collar bones; thin curved bones

    • posterior scapulae (2) = shoulder blades

Page 100:

• Clavicle

• Scapula

• Front

Page 101:

• Upper limbs (60 bones)

  • 2 humerus = upper arm bone: typical long bone

Page 102:

• Upper limbs

  • 2 Radius = forearm bone on same side as thumb

  • 2 Ulna = forearm bone on same side as pinky; extends from the elbow to the wrist

Page 103:

• Upper limbs – hand (27 bones)

  • 8 carpals (wrist; short bones in 2 rows)

  • 5 metacarpals (hand/palm; long bones)

  • Phalanges (plural); phalanx (singular) = finger bone or digit

    • Thumb (pollex) = 2 digits

    • Fingers = 3 digits

  • Total per limb = 14 digits or phalanges

Page 104:

• The appendicular skeleton

  • Pelvic (hip) Girdle = connects lower limbs to the vertebral column

    • 2 bones

    • pair of coxal bones which articulate:

      • anteriorly at the symphysis pubis, posteriorly with the sacrum

    • The socket which articulates with head of femur = acetabulum

    • The hole in each coxal bone is called the obturator foramen

Page 105:

• Pelvic (hip) Girdle

  • Each coxal bone consist of 3 fused bones in adults:

    • ischium = lowest L-shaped portion (i.e. area we sit on)

    • ilium

    • pubis = anterior portion of coxal bone; bladder rests on it

Page 106:

• Lower limbs

  • 2 Femur = thigh bone: largest, longest, strongest bone in skeleton; extends from the hip to the knee

  • 2 Tibia = shin bone: very strong

  • 2 Fibula = thin bone lateral to tibia

Page 107:

• Lower limbs (60 bones)

  • Tarsus = 7 tarsal (ankle) bones

    • Body weight is carried on 2 largest tarsals:

      • Talus = uppermost tarsal which articulates with the tibia and fibula

      • Calcaneus = heel bone

  • 5 metatarsal (foot) bones

  • Phalanges = toe bones or digits (14 total)

Page 108:

• Life Span Changes

  • Age related skeletal changes are apparent at the cellular and whole body level

  • Height begins to decreases incrementally age around age 33

  • Bone loss gradually exceeds bone replacement

  • After menopause, females lose bone more rapidly than males

  • By age 70, bone loss between sexes is similar

  • Fractures increase as bones age

Page 109:

• NEWBORN CHILD AGE

• Deterioration of vertebral support

• 6 NEXT ADULT AGE 35 NY NEXT ELDERLY AGE *ADAM 80 MY NEXT ANATOMY REXT

Page 110:

• Young Female

• Old Female

Page 111:

• Types of Joints

  • The classification of joints is based on:

    • what binds the bones together to form joints (anatomical classification)

    • the amount of space between the bones of a joint and the amount of movement it allows (functional classification)

Page 112:

• Anatomical Classification of Joints

  • fibrous joints

    • have no synovial cavity; bones held together by fibrous connective tissues

    • E.g., sutures of the skull; syndesmoses - Ligaments (clusters of fibrous connective tissue) hold these joints together e.g., the interosseous ligament holds the tibia

Page 113:

• Anatomical Classification of Joints

  • Gomphosis

    • between the teeth and their bony alveolar sockets

    • Crown of tooth

    • Gingiva (gum)

    • Root of tooth

    • Periodontal Gomphosis ligaments

    • Alveolar bone

Page 114:

• Anatomical Classification of Joints

  • cartilaginous joints

    • have no synovial cavities; held together by cartilage tissue

    • synchondrosis joints e.g., epiphyseal plate (growth plate) between the epiphysis and the diaphysis

    • Symphysis joints e.g., pubic symphysis and intervertebral joints

Page 115:

• Anatomical Classification of Joints

  • synovial joints

    • have a synovial cavity; held together by articular capsule and ligaments

    • Ends of the bones covered by hyaline cartilage and bound by the articular capsule that surrounds the articulating bones

    • The articular capsule is composed of dense connective tissue superficially and a deep layer of loose connective tissue called the synovial membrane

    • These joints are further stabilized by accessory structures such as ligaments

Page 116:

• Synovial joints

  • planar

  • hinge

  • pivot

  • condyloid

  • saddle

  • ball and socket

Page 117:

• Video Link

Page 118:

• Physiological Classification of Joints

  • the degree of movement that they have

  • synarthrosis joint - no movements

  • amphiarthrosis joints - small amount of movement

  • diarthrosis joints - freely moveable joints; variety of shapes and abilities in movements

Page 119:

• Movements

  • gliding

  • angular movements - change the angle between articulating bones

    • flexion

    • extension

    • abduction

    • adduction

    • circumduction

Page 120:

• Movements

  • rotation

  • pronation and supination

  • inversion and eversion; occurs at the ankles

  • elevation and depression

  • protraction and retraction

  • opposition

Page 121:

Page 122:

• Bursae

  • fluid-filled pouches; similar structure to the articular capsule

  • outer dense connective tissue superficially and a deep layer of loose connective tissue called the synovial membrane

  • contain small amount of fluid (similar to synovial fluid); located in areas of friction in synovial joints

  • Superficial bursae can be palpated in the knee and shoulder joints

Page 123:

• Tendons and ligaments

  • Tendons and ligaments are similar in structure consisting of bundles/cables of dense connective tissue containing collagen fibers

  • Ligaments differ slightly in that