Skeletal System Flashcards
Percentage composition of the bone from the body weight
20%
Skeletal system is composed of
interconnected system of bones, cartilage, joints, and associated ligaments.
Osteology
is the branch of science that deals with the study of the skeletal system structure and function
Bone composition
Bone connective tissue (Mineralized)
Cells: Osteocytes
Matrix: Collagen fibers within a matrix of calcium phosphate.
Bone function
Provides firmness and support.
(Can be compact or spongy.)
Cartilage composition
Cartilage Connective tissue
Cells: Chondrocytes
Matrix: Collagen fibres within a rubbery gelatinous substance called chondrin.
Cartilage function
-Covers bone tips and reduces friction.
-Provides smooth and flexible cushioning.
Ligament composition
Dense connective tissue
Cells: Fibroblasts
Matrix: Dense collagen fibers
Ligament function
Connects bone to bone, stabilizes joints.
(Holds bones together)
Function of the bones
Protects vital organs (such as the skull protecting the brain and vertebrae protecting the spinal cord)
Storage of fat and minerals (Ca)
Fat Storage: Bones serve as a storage site for fat, primarily within their internal yellow marrow cavity
Calcium and Phosphorous Storehouse: Most of the body’s calcium is stored in bones in the form of calcium salts.
Blood cell formation (Hematopoiesis): occur within the red marrow cavities of certain bones.
Movement:Skeletal muscles, when attached to bones, facilitate movement and act as mechanical force multipliers.
Support: Provides a hard framework that supports and anchors the soft organs of the body.
Why do we need a small amount of calcium ions (Ca2+) to be present in the blood at all times
To support various bodily functions, including:
1. Transmitting messages within the nervous system
2. Enabling muscle contraction
3. Supporting blood clotting (converting prothrombin to thrombin)
The movement of calcium is regulated by
Hormones
No. of bones at birth and in adulthood
270
206
Division of the skeleton system
Axial skeleton (80 bones)
Appendicular skeleton (126 bones)
Axial skeleton bones and function
Bones
Skull
Vertebral column
Thoracic cage
Function
Protection of the internal organs
The appendicular skeleton bones and function
Bones
Shoulder grindle
Upper limbs
Pelvic girdle
Lower limbs
Function
Facilitate movements
Types of bone tissues
Compact bone
Spongy bone
Description and function of the compact bone
Description
Dense, hard, smooth, homogenous
Function
Provide structural support
Description and function of the spongy bone
Description
Has a spiky, open appearance like a sponge
Function
Provide structural support and store bone marrow
Periosteum
Tough membrane that covers and protects the outside of the bone
Bones are classified according to their shape into ____ groups
Four
Bones shapes
Long - humerus
Short - talus
Flat - sternum
Irregular - vertebra
Long bones
mostly compact bone (the outside part) surrounding spongy bone (red marrow).
Inside a long bone is a medullary cavity filled with yellow bone marrow.
Long bones of the appendicular system
Upper limb - Humerus, radius, ulna, metacarpals, phalanges
Lower limbs - Femur, tibia, fibula, metatarsals, phalanges
Function: Supporting body weight and facilitating movement
What is the longest and heaviest bone in the body?
Femur
Short bones
• Are generally cube-shaped
• Contain mostly spongy bone
• Include bones of the wrist and ankle
• short bones provide stability and some movement.
Ex: carpals/ tarsals
Sesamoid bones
are a special type of short bone that form within tendons
Ex: patella
Flat bones
Are thin, flattened, and usually curved (protects internal organs)
Have two thin layers of compact bone that surround a layer of spongy bones
Examples
Cranial bones (skull)
Ribs
Sternum (breastbone)
Scapula
Irregular bones
Have irregular shape
Examples:
Vertebrae
Hip bones
Gross anatomy of a long bone (structures)
Diaphysis
Periosteum
Endosteum
Medullary cavity in adults
Medullary cavity in infants
Red Marrow in Adults
Epiphysis
Diaphysis
Main shaft of the bone (Composed of compact bone)
Periosteum
A layer of fibrous connective tissue covering the diaphysis; also involved in bone formation and repair
Endosteum
A layer of epithelial tissue lining the inside wall of the medullary cavity; houses bone cells
Medullary Cavity in Adults
Primarily contains yellowbone marrow, which serves as a storage area for adipose (fat) tissue
Medullary Cavity in Infants
Contains red marrow where blood cells are formed, playing a role in blood cell formation
Red Marrow in Adults
Confined to cavities in the spongy bone of flat bones and the epiphysis of some long bones
Location of the epiphysis
The ends of the bone
Composition of the epiphysis
Consists of a thin layer of compact bone enclosing an area of spongy bone (filled with red marrow) that produces red and white blood cells
External surface of the epiphysis
Covered by an articular cartilage, made of hyaline cartilage that decreases friction at joint surfaces
epiphyseal line is in what type of bones?
Adult bones
Epiphyseal line
is a remnant of the epiphyseal plate (a flat plate of hyaline cartilage seen in a young, growing bone)
Epiphyseal plates
cause the lengthwise growth of a long bone
Bone connective tissues cells
Osteocytes
Bone connective tissue matrix
• One-third is composed of organic components (collagen fibre), which provide bone flexibility and great tensile strength.
• Inorganic components mainly composed of hydroxyapatite (a form of calcium phosphate), it provides bones with rigidity and strength, making them resistant to compression
• Water 25%
The central (harvesian) canal
A compact bone tissue contains passageways (called central (harvesian) canal) carrying nerves, blood vessels, which provide the living bone cells with nutrients and a route for waste disposal.
Arrangement of Lacunae
Lacunae are arranged in concentric circles called lamellae
Lamellae are circles around the central (Haversian) canal
Haversian system
Each complex consisting of a central canal is called an osteon, or Haversian system.§ Because of this network of canals, bone cells are well nourished in spite of the hardness of the matrix, and bone injuries heal quickly.
The human skeleton is composed of two strong and supportive tissue
Cartilage
Bone
Ossification
Formation of Long Bone
In embryonic stages, the skeleton consists primarily of _________, but as fetal growth to continue, most of the cartilage is replaced by _______.
hyaline cartilage, bone
Ossification
Long bones develop using hyaline cartilage as a template
Ossification involve 2 phases in the
Embryo and fetus
Embryo phase
In the embryo, osteoblasts create a bone matrix cover ‘collar’ around the entire hyaline cartilage model
Fetus stage
In the fetus, the hyaline cartilage model is gradually replaced by bone tissue, and the central region is digested away, creating a medullary cavity within the newly formed bone
Postnatal bone formation
By birth or shortly thereafter, most hyaline cartilage models have been transformed into bone, except for two regions - the articular cartilages covering bone ends and the epiphyseal plates
Bone growth
Lengthwise
Sideways
Hormonal control
Bone growth lengthwise
Grow in length as infant develops into a child
- New Cartilage Formation: On the external face of the articular cartilage, and on the surface of the epiphyseal plate, new cartilage is consistently formed.
- Old Cartilage Replacement: At the same time, the old cartilage next to the inner part of the articular cartilage and near the medullary cavity is slowly broken down and substituted with bone material.
Bone Growth-sideways
• Osteoblasts in the periosteum build bone on the outer surface of the diaphysis.
• Osteoclasts in the endosteum simultaneously remove bone from the inner surface of the diaphysis.
• These two cell types work at a similar pace, resulting in the expansion of the long bone’s diameter, and the bone widens due to this coordinated activity of osteoblasts and osteoclasts. • This process by which bones increase in diameter is called appositional growth.
Bone Growth- Hormonal control
• The growth is controlled by growth hormone and, during puberty, the sex hormones.
• The growth ends during adolescence, when the epiphyseal plates are completely converted to bone (become epiphyseal line).
Are bone static structures or dynamic tissues?
They are dynamic tissues that continuously change
Bone remodeling occurs in response to two main factors:
1) The blood calcium levels.
2) The influence of gravity and muscle tension on the skeleton.
Hypercalcemia
In cases of high blood calcium levels (hypercalcemia), the thyroid gland releases calcitonin, which stimulates osteoblasts to deposit excess calcium into the bone matrix as hard calcium salts.
Hypocalcemia
When blood calcium levels decrease, the parathyroid glands release parathyroid hormone (PTH) into the blood. PTH activates osteoclasts, which break down bone matrix to calcium ions into the blood.
What happens to bones in bedridden or physically inactive individuals?
They tend to atrophy and lose mass.
Mechanism of Bone Remodeling- Type of cells
Osteoclast
Osteoblast
Osteocytes
Osteoclasts
multinucleated cells
destroy bones
They contain numerous mitochondria and lysosomes.
Osteoblasts
bone forming cells
uninucleated cells
Considered part of the periosteum.
Osteocytes
mature bone cells (inside the bone matrix).
found in lacunae between the concentric lamellae of osteons.
Resorption
Old bone is resorbed by osteoclasts in a process called resorption
Ossification
new bone”is deposited by osteoblasts in a process called ossification (bone formation).
Location of osteoclasts
present on the outer layer of bone, underneath the periosteum.
Resorptionprocess
Attachment of the osteoclast to the osteon begins the process of resorption.
The osteoclast then secretes collagenase and other enzymes important in the resorption process.
As a result, high levels of calcium, phosphate and products of collagen will be released into the extracellular fluid.
Mechanism of Bone Formation
After bone resorption by osteoclasts, “a new bone tissue” is deposited by osteoblasts.
Osteoblasts synthesize the organic(primary collagen and smaller quantities of proteins like osteocalcin and osteopontin) and inorganic components (by depositing calcium and phosphate-based minerals [Hydroxyapatite Ca5(OH)(PO4)3]) of the bone matrix.
Once the osteoblast is finished working, it either becomes trapped inside thehardened bone and becomes an osteocyte or becomes bone lining cells(periosteal and endosteal cells).
Bone fracture
Break in a bone
Main types of bone fractures
Closed (simple) fracture
Open (compound) fracture
Closed (simple) fracture
break that does not penetrate the skin
Open (compound) fracture
broken bone penetrates through the skin (bone punctures the skin)
Common Types of Fractures
Comminuted
Compression
Depressed
Impacted
Spiral
Greenstick
Comminuted
Bone breaks into three or more fragments
Particularly common in older people, whose bones are more brittle
Compression
Bone is crushed
Common in porous bones (i.e., osteoporotic bones of older people)
Depressed
Broken bone portion is pressed inward
Typical of skull fracture
Impacted
Broken bone ends are forced into each other
Commonly occurs when someone attempts to break a fall with outstretched arms
Spiral
Ragged break occurs when excessive twisting forces are applied to a bone
Common sports fracture
Greenstick
Bone breaks incompletely, much in the way a green twig breaks
Common in children, whose bones are more flexible than those of adults
Treatment of bone fractures
reduction (realignment of broken bones)
Immobilization
Two types of treatment by reduction
Closed reduction
Open reduction
Closed reduction
the bone ends are manually coaxed into their normal position by the physician’s hands.
Open reduction
surgery is performed, and the bone ends are secured together with pins or wires.
The greenstick fracture is treated by which type of reduction?
Closed reduction
After reduction
The bone is immobilized by a cast or traction to allow the healing process to begin.
Healing time
for a simple fracture is 6 to 8 weeks, but it is much longer for large bones and for the bones of older people (because of their poorer circulation).
The repair of bone fractures involves four major events
- Hematoma
- Fibrocartilage callus forms:
- The bony callus forms.
- Bone remodeling occurs
Hematoma
Blood vessels rupture when the bone breaks, leading to the formation of a blood-filled swelling known as a hematoma.
Fibrocartilage callus forms:
Connective tissue cells of various types form a mass of repair tissue known as the fibrocartilage callus. This callus contains several elements, including cartilage matrix, bony matrix, and collagen fibers, which serve to stabilize the broken bone, bridging the gap and promoting healing.
The bony callus forms.
As more osteoblasts and osteoclasts migrate into the area and multiply, the fibrocartilage callus is gradually replaced by the bony callus made of spongy bone.
Bone remodeling occurs
Over the next few weeks to months, depending on the bone’s size and site of the break, the bony callus is remodeled in response to the mechanical stresses* placed on it, so that it forms a strong, permanent “patch” at the fracture site.
Orthopedic devices
The use of external fixation devices, such as casts, splints, or braces, can influence the distribution of mechanical stress on the fractured bone during the healing process.
What type of tissue makes up the bony callus that replaces the fibrocartilage callus during bone healing?
Spongy bone
How does bone remodeling contribute to the healing of a bone fracture?
It gradually strengthens the bony callus
The skeleton is divided into 2 subdivisions
The axial skeleton
The appendicular skeleton
The axial skeleton
the bones that form the longitudinal axis of theVertebraVertebralcolumnRadiusUlnaSacrumBones ofpelvicgirdlebody
The appendicular skeleton
thebones of the limbs and girdles that are “appended” (attached) to the theaxial skeleton.
Axial skeleton is divided into 3 parts
Skull
Thoracic cage
Vertebral column
The skull have 2 sets of bones
Cranium bones
Facial bones
Cranium bones
enclose the brain
Facial bones
• Hold eyes in anterior position
• Allow facial muscles to express feelings
Bones of the skulls are joined by
Sutures
What is the only bone in the skull that is attached by a free movable joint?
Mandible
8 cranial bones that protect the brain
Frontal bone
Occipital bone
Ethmoid bone
Sphenoid bone
Parietal bones (two pairs on each side of the skull) Temporal bones (two pairs on each side of the skull)
14 facial bones in the skull
Paired facial bones (Maxillae, Zygomatic, Palatine, nasal, Lacrimal, inferior nasal conchae)
Unpaired facial bone (Mandible, Vomer)
Paranasal Sinuses
four paired air-filled spaces that surround the nasal cavity(frontal sinus, Ethmoid sinus, Sphenoidal sinus, and Maxillary sinus)
Functions of paranasal sinuses
– Lighten the skull
– Amplify sounds made as we speak
Thoracic cage function
protect major organs
Thoracic cage is made up of three main components:
Sternum
Ribs
Thoracic vertebrae
Ribs
True
False
Floating
True ribs
directly connect to the sternum via costal cartilage.
False ribs
do not directly attach to the sternum but may connect indirectly through shared costal cartilage with the true ribs.
Floating ribs
Do not attach to the sternum at all and only connect to the thoracic vertebrae.
Function of the vertebral column
provides axial support
Composition of the vertebral column
composed of 24 single vertebral bones separated by intervertebral discs
9 vertebrae fuse to form two composite bones
extends from the skull to the pelvis
Function of the intervertebral disc
act as cushions and allow for flexibility
24 single vertebrae bone
7 cervical vertebrae are located in the neck region.
12 thoracic vertebrae are situated in the chest region.
5 lumbar vertebrae are associated with the lower back.
9 vertebrae fuse to form two composite bones
The sacrum is formed by the fusion of 5 vertebrae.
The coccyx (tailbone) is formed by the fusion of 3 to 4 coccygeal vertebrae.
natural curves or curvatures types
- Primary curvatures
- Secondary curvatures
Primary curvatures
Natural curves
Present at birth
Convex anteriorly (arch forward)
2 primary curvatures in the spine
Thoracic curvature
Sacral curvature (sacral region, loest part of the spine)
True or false
The two primary curvatures (thoracic and sacral) produce the C-shaped spine of the newborn baby.
True
Secondary curvatures
develop as a child grows and begins to change their body position and posture.
These curvatures develop later in life and are not present at birth.
Convex posteriorly (arch backwards)
two secondary curvatures in the human spine:
Cervical curvature
Lumbar curvature
Cervical curvature
develops as a baby begins to lift its head and later learns to support it.
This curvature forms in the neck region of the spine
Lumbar curvature
develops as a child starts to walk and bear weight on their lower back.
It is located in the lumbar (lower back) region of the spine.
The appendicular skeleton
Composed of 126 bones
– Limbs (appendages)
– Pectoral girdle
– Pelvic girdle
The Pectoral (Shoulder) Girdle
It is composed of two bones that attach the upper limb to the axial skeletal.
1- Clavicle(collarbone)
2- Scapula(shoulder blade)
The Pectoral (Shoulder) Girdle Function
Light
Poorly reinforced grindle
Allows for a high degree of mobility in the upper limb.
Calvicle function
plays a crucial role in connecting the upper limb to the axial skeleton and provides support for the shoulder joint.
Scapula
Flat bone that articulates with the humerus (the bone of the upper arm) to form the shoulder joint. It also provides attachment points for various muscles involved in arm movement.
Bones of the Upper Limbs
– The upper arm consists of a single bone: the humerus.
– The forearm consists of two bones: the ulna and the radius.
Anatomical position of the ulna and radius
The ulna is the medial bone, located on the inner side of the forearm.
The radius is the lateralbone, found on the outerside of the forearm.
Hand components
Carpals (wrist)
Metacarpals (palm)
Phalanges (fingers and thumbs)
Number of carpals
8 in each hand
4 in each row
Number of metacarpals
5 per hand
Number of phalanges
14 per hand
3 per finger
(Except the thumb, which has only 2 phalanges)
Bones of the lower limb
• Femur—thigh bone
– The heaviest, strongest bone in the body
• The lower leg has two bones
1. Tibia—shinbone; larger and medially oriented
2. Fibula—thin and sticklike; lateral to the tibia
Has no role in forming the knee joint
Foot components
Tarsals
Metatarsals
Phalanges
Number of tarsals
7
1 Calcaneus (heel bone)
1 talus
5 smaller tarsals
Number of metatarsals
5 (form the sole of the foot)
Number of phalanges
14
Toes (3 phalanges in each toe, 2 big toe)
Bones of the Pelvic Girdle
Pelvic girdle = 2 coxal (hip) bones plus sacrum
Pelvis = 2 coxal (hip) bones, sacrum, and coccyx
Each coxal bone (hip bone) consists of ilium, pubis, and ischium, fused together.
Bones of the Pelvic Girdle Function
• The total weight of the upper body rests on the pelvis.
• The pelvis protects several organs, including the reproductive organs, urinary bladder, and part of the large intestine.
What is the primary function of the clavicle (collarbone)?
Preventing dislocation of the shoulder
Joints definition
Joints, also called articulations, are the sites where two or more bones meet.
Function of the bones
Hold the bones together securely.
Give the rigid skeleton mobility.
Classification of the joints
Functionally (immobile, slightly movable, freely movable)
Structurally (Fibrous, cartilaginous, and synovial)
Fibrous structural characteristics
Bone ends/parts united by collagenic fibers
Fibrous types
Suture (short fibres)
Syndesmosis (long fiber)
Gomphosis (periodontal ligament)
Suture (short fibres)
Type of fibrous joints found in the skull
The irregular edges of the skull bones interlock and are tightly bound together by connective tissue fibers
serve to protect the brain
Immobile
Syndesmosis (longer fibers)
Longer connecting fibres compared to sutures, this will allow slight movement
Present between the tibia and fibula bone, providing some mobility and shock absorption
Slightly mobile and immobile
Gomphosis (periodontal ligament)
Bind the roots of the teeth (the pegs) with their sockets in the mandible and maxilla
(Fibrous peg and socket joint)
They provide stability and support for the teeth
Immobile
Cartilaginous structural characteristics
Bone ends/parts united by cartilage
Cartilaginous types
Synchondrosis (hyaline cartilage)
Symphysis (fibrocartilage)
Synchondrosis (hyaline cartilage)
Immobile
Example
The cartilaginous joints between the true ribs and sternum
The hyaline cartilage epiphyseal plates of growing long bones
Symphysis (fibrocartilage)
Slightly movable
Example
Intervertebral joints of the spinal column where the articulating bone surfaces are connected by pads (discs) of fibrocartilage
Pubic symphysis of the pelvis
Synovial structural characteristics
Bone ends/parts covered with articular cartilage and enclosed within an articular capsule lined with synovial membrane
Synovial types
Plane
Hinge
Pivot
Condylar
Saddle
Ball and socket
Plane joint
Nonaxial (no direction/ movement)
Ex: intercarpal joints
Intertarsal joints
Hinge joint
Uniaxial
Ex: elbow joints
Interphalangeal joints
Pivot joint
Uniaxial
Ex: proximal joint between the radius and the ulna
Condylar joint
Biaxial
Knuckles
Saddle joint
Biaxial
Carpometacarpal joint of the thumb
Ball and socket joint
Multiaxial
Shoulder joints
Hip joints
Synovial joints definition
Joints in which articulating bone ends are separated by a joint cavity with synovial fluid.
Synovial joint distribution
Found in all the limbs
Synovial joint function
Synovial fluid within the joint cavity provides lubrication, nourishment, and shock absorption for smooth and pain-free movement.
Features of synovial joint
Articular cartilage
Articular capsule
Joint cavity
Reinforcing ligaments
Articular cartilage
articular (hyaline) cartilage covers ends of bones forming the joints.
Articular capsule
The joint surfaces are enclosed by a sleeve or layer of fibrous connective tissue, which is lined with a smooth synovial membrane (the reason these joints are called synovial joints)
Joint cavity
The articular capsule encloses a cavity, called the joint cavity, which contains lubricating synovial fluid.
Reinforcing ligaments
The fibrous layer of the capsule is usually reinforced with ligaments.
Bursa and tendon sheath
closely associated with the synovial joints
Bursa and tendon sheath function
They help cushion and reduce friction between adjacent structures during joint acti
Bursae
Are flattened fibrous sacs lined with synovial membrane and containing a thin film of synovial fluid. They are common where ligaments, muscles, skin, tendons, or bones rub together
Tendon sheath
ls an elongated bursa that wraps completely around a tendon subjected to friction
