Anatomy: Skeletal System

• The skeleton consists of 206 bones that provide a framework, support, and protection for the body and must be linked together to allow movement
• Joints are the links between bones, where ligaments hold bones together for stability and flexibility
• Muscles and tendons facilitate movement at joints

Objectives of Studying Bone

• Functions of the skeleton
• Structure of bone
• Growth and development of bone
• Different types of bone in the body
• Names and positions of the bones of the skeleton
• Different types of joints and their range of motion
• Importance of good posture
• Postural defects
• Common pathologies of the skeletal system
• Interrelationships between the skeletal and other body systems

Functions of the Skeleton

• Osteology is the study of the structure and function of bones.

• The mnemonic "Pam's skeleton forces movement" can help remember bone functions: protection, attachment, movement, support, shape, formation of blood cells, mineral reservoir

• Protection: The skeleton protects vital organs and tissues. Example: the rib cage protects the heart and lungs

• Attachments: Bones provide strong attachment sites for muscles and tendons

• Movement: Bones act as levers for muscles, aiding in coordinated movement

• Support: The skeleton bears the weight of all other tissues, example bones of the vertebral column, pelvis, feet and legs support the body

• Shape: The skeleton gives shape to structures like the skull, thorax, and limbs

• Formation of blood cells: Blood cells are developed in red bone marrow found in cancellous bone tissue

• Mineral Reservoir: The skeleton stores minerals, such as calcium, which can be released when needed for metabolic processes

Structure of Bone

• Bone is a hard connective tissue containing water, collagen fibers (for tensile strength), and mineral salts such as calcium and phosphate (for hardness)
• Osteoblasts: Bone tissue is living and made from cells called osteoblasts
• Compact bone: the main shaft of long bones, the outer layer of other bones and protects inner cancellous bone and allows the skeleton to provide a firm framework
• Cancellous bone: more porous and lighter than compact bone, which is found at the ends of long bones and in the center of other bones

Compact Bone Makeup

• Osteocytes are bone cells in concentric rings called lamellae around a central Haversian canal
• Haversian canals: Small tubes that form a network in bone for nerves, blood, and lymphatic vessels to pass

Cancellous (spongy) Bone

• Structure: it has an open sponge-like appearance
• Location: found at the ends of long bones and in the center of other bones
• Haversian System: it does not have a Haversian system
• Composition: a web-like arrangement of spaces filled with red bone marrow and separated by thin processes of bone
• Blood Vessels: carry nutrients and oxygen through every layer

Bone Marrow

• Bones contain red and yellow marrow
• Red Marrow: manufactures red blood cells; it is located at the end of long bones and at the center of the bones of the thorax and pelvis
• Yellow Marrow: mainly a fatty tissue, found chiefly in the central cavities of long bones

Long Bone Structure

• Diaphysis: the long central shaft
• Epiphysis: larger, rounded ends of long bones
• Epiphyseal Cartilage: the site of bone elongation during growth years, located between the diaphysis and epiphysis; replaced by compact bone between 18 and 25 years of age
• Medullary canal/cavity: a hollow center of the bone shaft, containing red and yellow bone marrow
• Periosteum: a thin membrane of connective tissue covering bones (except the ends that form joints); its outer layer is dense with blood vessels, and its inner layer contains osteoblasts

Cartilage

• Structure and Function: smooth hyaline cartilage covers the articular surfaces of long bones is firm and elastic, which provides shock absorption and has no neural or vascular supply

Development of Bone

• Ossification: bone development; fetal bones are cartilage rods that turn into bone as a child grows
• Ossification occurs in 3 stages: the cartilage-forming cells (chondrocytes) enlarge and arrange themselves in rows, then calcium salts are laid down by bone-building cells (osteoblasts), and cartilage-destroying cells (osteoclasts) enable the absorption of unwanted bone
• Oestrogen and testosterone spur bone growth in teenagers
• Adults vs Children: Children's bones are more flexible but in older adults bone cells outnumber cartilage cells and bone becomes more brittle, contains more minerals and fewer blood vessels

Bone Cells

• Chondrocytes: The cartilage-forming cells
• Osteoblasts: Bone-building cells that lay down calcium salts
• Osteoclasts: Cartilage-destroying cells that enable absorption of unwanted bone
• Osteocytes: mature bone cells that maintain bone throughout life
• Weight-bearing exercises increase osteoblast (bone-building cell) activity

Cartilage Makeup

• Cartilage: a dense connective tissue with collagen and elastin fibers embedded in a gel-like substance that can cushion and absorb shock and prevent direct damage to bones

Cartilage Types

• Hyaline: covers the articular bone surfaces
• Fibrous: a strong and rigid type of cartilage found between the discs of the spine
• Elastic: a very flexible type of cartilage found in the auditory canal of the ear
• Cartilage does not repair or renew easily since it does not have a blood supply

Ligaments

• Ligaments: dense, strong, and flexible bands of white fibrous connective tissue that link bones together at joints, allowing bones to move freely within a safe range

Tendons

• Tendons: tough, white, fibrous cords of connective tissue that attach muscles to the periosteum of a bone, enabling bones to move when skeletal muscles contract

Bone Types Defined by Shape

• Long Bones: weight-bearing bones that provide structural support examples are arms and legs
• Short Bones: cube-shaped bones that provide support and stability with little movement, examples are wrist and ankle bones
• Flat Bones: plate-like structures that provide protection, examples are ribs and scapulae
• Irregular Bones: bones with various shapes, often with projections for muscle/tendon/ligament attachment; examples are vertebrae and facial bones
• Sesamoid Bones: small, rounded bones embedded in a tendon, example is the kneecap

Other Bone Information

• The smallest bones are in the ear: hammer, anvil, and stirrup
• Long bones have a long shaft (diaphysis) and one or more endings or swellings (epiphysis)
• Bone surfaces are not always smooth and have bumps, lumps, dips, and ridges

Bone Surfaces and examples

• Acetabulum: A concave surface of a pelvis that forms the hip joint.
• Crest: A large ridge of bone.
• Condyle: Round (knuckle-shaped) prominence at the end of a bone, often part of a joint.
• Depression (fossa): A hollow, usually in a bone.
• Epicondyle: A smaller expansion of bone over a condyle.
• Facet: A small, shallow depression articulating with another bone.
• Foramen: An opening or passage, especially in a bone.
• Head: A rounded end of a bone.
• Process: A general term for any prominence or prolongation from a bone.
• Protuberance: Knob-like protrusion of a bone
• Spine: Sharp, slender projection of a bone.
• Trochanter: Large, blunt bump-like projection
• Tubercle: Rounded projection, usually blunt and irregular
• Tuberosity: Large, rounded rough projection, often serving as a muscle/ligament attachment point

The Skeletal System Divisions

• Composed of 2 parts
  • Axial Skeleton (80 bones): the main axis or central core of the body
  • Appendicular (126 bones): the appendages (limbs) and where they attach to the axial skeleton

Skull

• Weighs around 5kg and includes the 8 bones of the cranium and 14 bones of the facial skeleton
• The skull encloses and protects the brain and provides surface attachment points for muscles of the face, jaw, and neck

Skull Bones

• Frontal × 1: Anterior part of the roof of the skull, the forehead, and the upper part of the orbits (eye sockets).
• Parietal × 2: Upper sides of the skull and the back of the roof of the skull.
• Temporal × 2: Sides of the skull below the parietal bones and above and around the ears.
• Sphenoid × 1: In front of the temporal bone and serves as a bridge between the cranium and the facial bones.
• Ethmoid × 1: Part of the wall of the orbit, the roof of the nasal cavity, and part of the nasal septum.
• Occipital × 1: The back of the skull

Sutures of the Skull

• Coronal: joins the frontal bone to the parietal bones
• Sagittal: joins the two parietal bones to one another
• Lambdoid: separates the parietal bones from the occipital bones
• Squamous: separates the parietal bone from the temporal bone

Facial Bones

• Maxilla x 2: largest bones of the face; form the upper jaw and support the upper teeth.
• Mandible x 1: only movable bone of the skull; forms the lower jaw and supports the lower teeth; the largest and heaviest bone in the skull
• Zygomatic x 2: most prominent of the facial bones; form the cheekbones

More About The Face

• Nasal x 2: these small bones form the bridge of the nose.
• Lacrimal x 2: The smallest of the facial bones, located close to the medial part of the orbital cavity
• Turbinate x 2: Layers of bone located either side of the outer walls of the nasal cavities.
• Vomer x 1: single bone at the back of the nasal septum.
• Palatine x 2: L-shaped bones which form the anterior part of the roof of the mouth.

Hyoid Bone

• Location and Description: a U-shaped structure located in the anterior neck at the base of the mandible that it acts as a site of attachment for the anterior neck muscles

Sinuses Structure and Function

• Sinuses: four pairs of air-containing spaces in the skull and face that lighten the head, produce mucus, and act as resonance chambers for sound
• Frontal Sinuses: In the forehead, above the eyes and nasal bridge
• Ethmoidal Sinuses: located behind the eyes and in the deeper recesses of the skull
• Sphenoidal Sinuses: located behind the ethmoid sinuses
• Maxillary Sinuses: The largest sinuses are located on either side of the nostrils in the cheekbone area

Vertebral Column

• Extends from the skull to the pelvis and provides a central axis to the body, consists of 33 individual irregular bones (vertebrae), but the bones of the base of the vertebral column (sacrum and coccyx) are fused to create 24 movable bones

Function of the Vertebral Column

• Provides a strong and slightly flexible axis
• Surface for muscle group attachment
• Protects nerve pathways

Vertebrae Regions

• Cervical (7 vertebrae): vertebrae of the neck; C1(atlas) and C2(axis) allow the head and neck to move freely
• Thoracic (12 vertebrae): vertebrae of the mid-spine, lie in the thorax where they articulate with the ribs, lie flatter and downwards to allow for muscular attachment of the large muscle groups of the back
• Lumbar (5 vertebrae): vertebrae of the lower back; they are much larger, designed to support more body weight
• Sacral (5 fused bones/sacrum): lies between the pelvic bones; very flat and triangular shaped bones
• Coccygeal (4 fused bones/coccyx): base of the spine below the sacrum that are sometimes referred to as the coccyx (tail bone)

Intervertebral Discs

• Fibrocartilage pads between vertebrae, providing flexibility and shock absorption

The Thoracic Cavity

• Protects the heart and lungs
  • Sternum: sometimes referred to as the breast bone that is a flat bone lying just beneath the skin in the centre of the chest.
    • Manubrium: the top section which articulates with the clavicle and the first rib
    • Gladiolus: the main and longest part located in the middle, which articulates with the costal cartilages that link the ribs to the sternum
    • Xiphoid process: the bottom section, which provides a point of attachment for the muscles of the diaphragm and the abdominal wall.

Ribs Anatomy

• Ribs: 12 pairs that articulate posteriorly with the thoracic vertebrae with the first 10 pairs that attach to the sternum via the costal cartilages
  • True ribs: the first seven pairs and attach directly
  • False ribs: the remaining three and attach indirectly
  • Floating ribs: the last two have no anterior attachment

Appendicular Skeleton Makeup

• Supports the body's appendages: -The shoulder girdle
  • Bones of the upper limbs
  • Bones of the lower limbs
  • Bones of the pelvic girdle

Shoulder Girdle Anatomy

• Connects the upper limbs with the thorax that consists of two scapulae and two clavicles
  • Scapula: large flat bone, triangular that forms the posterior part of the shoulder girdle
    • Landmark locations: Between the second & seventh ribs
    • Features: acromion process: a large bony projection on the superior end of the scapula, spine, glenoid cavity
  • Clavicle: a long, slender bone with a double curve that forms the anterior portion of the shoulder girdle and acts as a brace to hold the arm away from the top of the thorax

Bones of the Upper Limb

Consists of: - Humerus: long bone in the upper arm - Radius: long bone of the forearm - Ulna: long bone of the forearm - Carpals: 8 bones forming the wrist - Metacarpals: 5 long bones forming the palm of the hand - Phalanges: 14 bones forming the fingers and thumb

Forearm Anatomy

• Radius and Ulna: long bones bound together by a fibrous ring that allow for rotating that can pass over each other
  • Ulna: bone of the little-finger side of the forearm
  • Radius: on the other hand situated on the thumb side of the forearm

Movements of Radius and Ulna

• Pronation: radius moves obliquely across the ulna, thumb side of hand closest to the body
• Supination: thumb side of the hand to the lateral side

Wrist and Hand

• Carpals: 8 irregularly shaped bones collectively called carpals, arranged in two groups of four that are held in place by ligaments; the upper row articulates with the ulna and the radius, while the lower row articulates with the metacarpals
  • Scaphoid, lunate, triquetral, and pisiform: bones of the upper row
  • Trapezium, trapezoid, capitate, and hamate: bones of the lower row
• Metacarpals: 5 long metacarpal bones in the palm, proximal ends articulate with the wrist bones, and distal ends with the finger bones Phalanges 14 and there are two in the thumb or pollex and three in each of the other digits

The Lower Limb Made Up Of

• Femur: Long bone forming the thigh
• Patella: Bone forming the kneecap
• Tibia: Long bone of the lower leg (anterior, medial side)
• Fibula: Long bone of the lower leg (lateral side)
• Tarsals: Seven bones forming the ankle
• Metatarsals: Five bones forming the dorsal surface of the foot
• Phalanges: Fourteen bones forming the toes

Thigh Facts

• Femur: the longest bone in the body with a shaft and two swellings at each end; the proximal swelling has a rounded head that fits into the socket of the pelvis to form the hip joint
• Patella: anterior to the knee joint with a main function to provide stabilisation and cushion and provide hinge for the knee joint and protect

Lower Leg Anatomy

• Tibia: anterior and medial side of the lower leg that has a large head where it joins the knee joint and forms part of the ankle
• Fibula: lateral side of the tibia and is shorter/thinner than the tibia forming part of the ankle on the lateral side.

Arches Of The Foot

• Three arches of the feet are designed to support body weight and provide leverage when walking
• Medial longitudinal arch runs along the medial side of the foot from the calcaneum bone to the end of the metatarsals
• Lateral longitudinal arch runs along the lateral side of the foot from the calcaneum bone to the end of the metatarsals
• Transverse arch runs between the medial and lateral aspect of the foot and is formed by the navicular, three cuneiforms, and the bases of the five metatarsals

Foot And Ankle

• Tarsals: the seven bones that are collectively called tarsals, each acts as an irregular bone to provide motion
  • Talus: the main tarsal that articulates with the tibia and fibula to form the ankle joint and bears the weight of the entire body when standing or walking
  • Calcaneum: heel bone that is an important site for attachment of muscles of the calf
  • Cuboid: situated between the fourth and fifth metatarsals and the calcaneum on the lateral (outer) border of the foot
  • Cuneiforms: the three cuneiform located between the navicular bone and the first three metatarsal bones
  • Navicular: the navicular bone is situated between the talus bone and the three cuneiforms
• Metatarsals 5 bones that form the dorsal surface of the foot
• Phalanges: 14 that make up the toes, two in the hallux (big toe), and three in each of the other digits.

The Pelvic Girdle

• Consists of two hip bones (innominate bones) joined at the back by the sacrum and at the front by the symphysis pubis Each hip bone consists of 3 separate bones: • Ilium: the superior (upper) part of the pelvic girdle; the iliac crest is the upper border and an important site of attachment for muscles of the anterior and posterior abdominal walls • Ischium: the inferior (lower) and posterior (back) part of the pelvic girdle; the ischial tuberosity is a bony protrusion that you sit on that receives the weight of the body when sitting • Pubis: collective name for the two pubic bones in the most anterior (forward) portion of the pelvis.

There are four joints or articulations within the pelvis

• Sacroiliac joints (x2) – located between the ilium of the hip bones and the sacrum
• Sacrococcygeal symphysis – found between the sacrum and the coccyx
• Pubic symphysis – located between the pubis bodies of the two hip bones
• Functions of the pelvic girdle: supports, helps bear weight, and protection

Bone Joints

• Point where two or more bones/cartilage meet (also called an articulation
• Bones act as levers with the joints the joints act as fulcrums

Joints by Classification

• Fibrous: a no movement is possible (so also known as a fixed joint)
• Cartilaginous: slight movement is possible
• Synovial: freely movable joints

Fibrous Joints

• Immovable joints where tough fibrous tissue between the bones (edges of bones dovetailed, as in skull sutures)

Cartilaginous Joints

• Slightly movable joints with a pad of fibrocartilage between the ends of the bones acting as shock absorbers [i.e. vertebrae of the spine and where the pubis bones meet, symphysis pubis)

Synovial Joints

• Freely movable joints with a more complex structure than fibrous or cartilaginous joints
  • Space is between the articulating bones called synovial cavity
  • Surface of articulating bones is covered by hyaline cartilage
  • Synovial cavity and cartilage are encased in fibrous capsule to hold bones together and enclosing the joint
  • Synovial membrane- inner layer of joint capsule that secretes synovial fluid to lubricate the joint and nourish cartilage.
  • Hyaline Cartilage: does not have a direct blood supply to give delivers oxygen and nutrients and to remove waste.

* Types of Synovial Joints* Movement Examples

 -Ball and Socket - Formed when the rounded head of one bone fits into aAllows movement in many hip and shoulder joints
 -Hinge  - Where the rounded surfaceof one bone fits the hollowMovement is only possible in one- Knee and elbow joints
 -Condyloid  - The joint surfaces are shapedAllow a condyloid joint the wrist joint
 -Gliding  - Often referred to as synovialplane joints as these occurAllow only a gliding motion in- joints between vertebrae
  -Pivot  - Occurs where a process ofbone rotates in a socketOnly permits rotation- joints between the first and  second cervical vertebrae
  -Saddle  - Shaped like a saddle the thumb joint

Types of Joint Movements

• Flexion: Bending of a body part at a joint so that the angle between the bones is decreased
• Extension: Straightening of a body part at a joint so that the angle between the bones is increased
• Dorsiflexion: Upward movement of the foot so that the feet point upwards
• Plantarflexion: Downward movement of the foot so that the feet face downwards towards the ground
• Adduction: Movement of a limb towards the midline
• Abduction: Movement of alimb away from the midline
• Rotation: A movement of a bone around an axis (180 degrees)
• Circumduction: Circling of joints 360 degrees
• Supination: Turning the hand so that the palm is facing upwards
• Pronation: Turning of the hand so that the palm is facing downwards

Posture

• Posture describes body alignment and balance and relies on the strength/tone of body muscles working against gravity
• when the maximum efficiency of the body is maintained with the minimum effort
• Draw an imaginary line vertically through the body, where good standing posture features these attributes: - feet together, contact on ankles/knees - hips are on the same level - shoulders are level - sternum/vertebral column- a center straight line - an erect/nontilted head

Poor Posture Causes

• Altered body functions, wasted energy, fatigue, increased risk of backache and headaches, impairs breathing, risk of muscular/ligament/joint(s) injury, digestion and/or circulation affected and a poor physical appearance

Postural Definitions

-An abnormally increased outward curvature of the thoracic spine with appearance of the back being rounded -Lodosis is-An abnormally increased inward curvature of the lumbar spine -Scoliosis is - A lateral curvature of the vertebral column

Skeletal Pathologies

• Ankylosing Spondylitis: a systemic inflammation to the intervertebral spaces that may lead to fibrosis, ossification, and stiffening of joints as the spine becomes rigid
• Arthritis: Gout- joint disorder due to deposition of uric acid crystals in the joint cavity
• Osteoarthritis-Joint disease known also as degenerative arthritis characterized by breakdown, growth of bony spikes & swell of the membranes.
• Rheumatoid – chronic inflammation of the peripheral joints due to pain/joint damage.
• Hallux Valgus: A swelling of the joint between the big toe leading to first metatarsal.
• Bursitis This condition due to injury.
• Contracture can lead to curvature of ring/finger fingers.
• A fracture is a beak of broken bone due to accident/injury and there are types: simple, impacted, complicated, and comminuted.

Further Skeletal Pathologies

• Frozen Shoulder/ Adhesive Capsulitis is a chronic condition leading to stiffness or joint shoulder problems.
• Hammer toe can be deformity of toes
• Osteoporosis condition of brittle bone leading to fracture.
• Spinal Bifida/ congenital defect of the column is cause midline fusion failure.
• Strains: sprains cause injury leading to tear. Ankle of the joints sprained leading to lower pain.
• Stress from injuries can affect the physical and emotional health Synovitis-This is inflammation of the joints that surround a synovial membrane. TMI Syndrome - A collection of sign disorders from Temporomandibular joints leading tenderness and bilateral motion. Whiplash- Condition damage due to accident around a sudden extension of the cervical spine.

Interrelationships With Other Systems

• The bone linking to the follow body systems:
• Skin-Vitamin D is produced it as roles with calcium absorption
• Muscular- Muscles connect bones leading movement joints
• Circulatory- Bones produce bone long
• Digestive- the digestive function breaks nutrients such as calcium
• Nervous-Skeletal needs to produce impulse
• Endocrine- Growth production happens in child.