PSK4U - Unit 2 Review

Skeletal System

The human skeleton consists of 206 bones (on average). Babies are born with about 305 bones but these fuse together over time (ie. skull, spine...). In utero, bones begin as cartilage and ossify (become harder) as the child gets older.

Function of Bones (x5)

Support - A stiff structure for soft tissues like muscles and organs

Movement - Bones provide the leverage for muscles to produce movement

Protection - Helps prevent soft tissue injury. Bone fractures are more easily (and better) repaired

Blood Production - Bone marrow produces blood cells (red, white, and platelets

Mineral Storage - Required minerals such as calcium and phosphorus are kept in bone for later use

Bone Composition (x2)

Collagen - Collagen is a series of rope-like fibers that provide a base network. This gives bone its flexibility

Apatite - Apatite is a collection of minerals (mainly phosphorus and calcium) that covers the collagen. This gives bone its strength

Collagen

Collagen is a series of rope-like fibers that provide a base network. This gives bone its flexibility

Apatite

Apatite is a collection of minerals (mainly phosphorus and calcium) that covers the collagen. This gives bone its strength

Bone Remodeling

Bone are not only strong and flexible, they can also repair themselves. The periosteum is a connective tissue that covers bone and contains two important cells that continuously repair and upgrade bone. Osteoblasts and osteoclasts

Osteoblasts

Osteoblasts are cells that lay down new bone material where damage or weakness is sensed.

Children have layers of osteoblasts in the shape of plates at the ends of their bones. These are called “growth plates”.

Osteoclasts

Osteoclasts are cells that break down bone material for the purposes of proper shaping or mineral needs.

Use for fracture or when minerals are needed in the blood stream.

Bone Modeling

Bones that are regularly subjected to weight-bearing physical activity tend to become denser and more mineralized than bones that are inactive.

Osteocytes

Osteocytes (used up osteoblasts) are embedded in the bone tissue to become the ‘sensors’ for stress on bones and signal increased or decreased osteoblast activity.

Types of Bones (x5)

Long, Short, Flat, Irregular, Sesamoid

Long Bone

Bones whose length significantly exceed their diameter (ie. femur, humerus). They contain both spongy and compact bone.

Short Bone

Bones that are small and often square in shape (ie. carpals, tarsals). They consist mainly of spongy bone. These are often "load-bearing" bones.

Flat Bone

Bones that are thin, wide and often in areas protecting vital organs (ie. skull, ribcage).

They also produce more blood cells than other bone types.

Irregular Bone

Bones that have odd shapes or patterns (ie. vertebrae or sacrum).

Sesamoid Bone

Bones that are small and wrapped in tendon material (ie. patella).

Anatomy of a Long Bone

Cartilage

This type of cartilage is referred to as articulating cartilage as it protects the points of articulation (where two bones meet).It allows for smoother movement at joints.

Periosteum

Thin layer of connective tissue that covers bone. Contains cells for bone re-modelling and is the connecting point for tendons and ligaments.

Medullary Cavity

Hollow part of bone shaft where bone marrow produces blood cells.

Compact Bone

Dense, rigid bone usually on bone shaft (diaphysis)

Spongy Bone

Compressive, flexible bone usually on bone ends (epiphysis). The trabeculae running throughout gives the bone its load-bearing capability and 'spongy' look.

Epiphyseal Plates

Site where most bone growth occurs. Contains a higher concentration of osteoblasts.

Bone Landmarks

Bones often have prominent features called landmarks. These may be ridges, grooves, depressions, or other surface markers on a bone. These can be a point of attachment or allow space for other systems.

Names of landmarks include crest, spine, tuberosity, condyle, fossa…

Types of Skeleton (x2)

The human skeleton is broken down into two main parts:

Axial Skeleton - This includes the skull, ribcage, and vertebral column (spine).

Appendicular Skeleton - This includes all the bones articulating with the arms and legs.

Axial Skeleton consists of:

Skull, Vertebra, Ribs, and Sternum

Skull is formed by 2 sets of bones:

Cranial and Facial

Cranial Bones (x8):

Ethmoid (1), Sphenoid (1), Frontal (1), Parietal (2), Temporal (2), Occipital (1)

Facial Bones (x14):

Vomer (1), Zygomatic (2), Palatine (2), Nasal (4), Lacrimal (2), Maxilla (2), Mandible (1)

Fontanelle

Membrane filled spaces between bones on infant skulls

Anterior fontanelle closes after about 18 months

Spine consists of:

Cervical Vertebrae (7), Atlas (C1), Axis (C2), Thoracic Vertebrae (12), Lumbar Vertebrae (5), Sacrum (1) (5 fused), Coccyx (1) (3-5 fused)

Vertebrae (The Spine)

• Born with 33 vertebrae, but those at bottom of spine fuse together to form the sacrum and coccyx

• Adult backbone consist of 26 separate vertebrae

• Each vertebrae is separated by an “intervertebral disk”

• Intervertebral disks prevent bones from grinding against each other and provides cushion to absorb shock when we move

• Excluding the sacrum and coccyx

• Spine has curves to help absorb shock

• cervical curve = lordotic,

• thoracic curve = kyphotic,

• lumbar curve = lordotic

• sacrum and coccyx = kyphotic

Scoliosis

Kyphosis

Lordosis

Vertebrae

• Vertebrae (except top 2) have a thick body to bear weight and two lamina that join and form a ring = vertebral arch

• Ring opening is called vertebral foramen = where spinal cord passes through

• Vertebra have processes that act as anchors for muscle attachment, shields to protect spinal cord

Cervical Vertebrae (7)

Smallest and lightest

C1-C7

Atlas (C1)

• Atlas has no body

• Superior surface of its transverse processes contain large depressions that receive occipital condyles of skull

• Yes!

Axis (C2)

• Axis (C2) acts as pivot for rotation of Atlas and skull

• No!

Atlas and Axis

Thoracic Vertebrae (12)

• Head of ribs articulate with bodies of vertebrae

• Tubercles of ribs articulate with transverse processes

Lumbar Vertebrae (5)

• Massive block-like bodies

• Weight bearing and thick

Sacrum (1) (5 fused)

• Fusion begins around age 20

• Forms posterior wall of pelvis

• Vertebral canal continues as sacral canal

Coccyx (1) (3-5 fused)

• Irregular vertebrae

• Commonly known as tailbone

Hyoid Bone

• Movable

• Horseshoe shape

• Located above Adams apple in men

• Attachment point for movement of larynx

• Gagging

• Sound

• Swallowing

• Foundation for tongue

• Breathing

• Keeping mouth open

Ribs

• Thorax is made up of sternum, ribs, and thoracic vertebrae.

• Thoracic vertebrae attach to ribs posteriorly

• Sternum attaches to ribs anteriorly

• First 7 pairs are true ribs because they attach directly to sternum by costal cartilage

• Next 5 pairs are false ribs because the attach indirectly to sternum

• Last 2 pairs of false ribs lack attachment so are called floating ribs

• Aid in breathing

Sternum

• 3 fused bones (manubrium, body, and xiphoid process)

• Attached to first 7 pairs of ribs

• Helps protect the heart, lungs, and major blood vessels from injury

Tuberosity

Obvious bump/protuberance on a bone that serves as a site for muscle or ligament attachment

Tubercle

Same as tuberosity, but smaller

Process

Projection of bone

Spine

Bone projection that is longer and thinner than a tuberosity

Fossa

Hollowed area of a bone

Foramen

Hole that passes through a bone

Condyles

Articular surfaces of bone

Mastoid Process

Sutures of the Skull (x4)

• Coronal Suture

• Lambdoid Suture

• Squamous Suture

• Sagital Suture

Fontanelles (x2)

• Anterior Fontanelle

• Posterior Fontanelle

External Auditory Meatus

Foramen Magnum

entry/exit of spinal cord

Functions of Muscular System (x3)

Locomotion - All body movements and many body functions (arms, heart, intestines…)

Posture - Even when relaxed muscles are working to keep you upright (neck, lower back…)

Heat Production - Body needs a basal temperature and muscles keep this by releasing heat as a by-product of reactions

Characteristics of Muscular System (x4)

Irritability - Sensitive to nervous stimuli

Contractility - Responds to stimuli by shortening

Extensibility - Can be stretched when relaxed

Elasticity - Return to normal length when relaxe

Muscle Tissue (3 types)

Smooth, Cardiac, and Skeletal Muscle

Smooth Muscle

• Usually found in hollow internal organs (stomach, intestines, bladder)

• Smooth muscle cannot be consciously contracted therefore it is said to be an involuntary muscle

• Smooth muscle lacks the appearance of striations

• Smooth muscle cells are shorter than skeletal muscle cells

Cardiac Muscle

• Occurs only in the heart

• Controlled involuntarily

• Can continue to function without nerve impulses

• They are striated in appearance and the cells are joined end to end

Skeletal Muscle

• Over 600

• Contraction is voluntary

• Striated in appearance (alternating dark and light bands)

• When stimulated by a nerve fibre it contracts and relaxes

• Includes both fast twitch and slow twitch fibers

• They are attached to bones and are responsible for movement

• Also used in talking, breathing, swallowing and singing

Actions of Muscular System

The movement a muscle causes depends on where it is attached to a bone and how it is crosses a joint

Origin

Immovable end (proximal end)

(When a muscle contract its insertion is pulled toward its origin)

Insertion

The moveable end of the joint (distal end)

(When a muscle contract its insertion is pulled toward its origin)

Muscles

Muscles that move in a specific manner are called AGONISTS (prime movers) whereas muscles that move opposite to the agonists are called ANTAGONISTS. Many muscles are paired in agonist – antagonist relations

(eg. Bicep and Tricep)

Muscle Development

Most muscles have formed by the 8th week of pregnancy. Most women can feel movement by the 17th week of pregnancy. At birth you have a fixed amount of muscle cells.

Growth of muscle cells depend on their use.

➔ Atrophy – decrease in muscle cell diameter due to neglect of stimulation

➔ Hypertrophy – increase in muscle cell diameter due to stimulation

Muscle Fibre Types

Within every skeletal muscle there are two types of fibres:

• Slow Twitch (Type 1) - required for endurance (eg. long-distance running, swimming, cycling…)

• Fast Twitch (Type 2) - required for quick bursts of power and energy (eg. sprinting, jumping, weight-lifting…)

Fast Twitch Fibres

Fast Twitch fibres (Type 2) can be further broken down into Type 2a and Type 2b.

Type 2a = Fast Oxidative

Type 2b = Fast Glycolytic

Type 2a = Fast Oxidative

These fibres can access both anaerobic and aerobic energy systems, and so are a hybrid of slow and fast twitch fibres. They produce fast contractions but are less fatigue resistant than Type 1 fibres.

Type 2b = Fast Glycolytic

These fibres can only access the anaerobic energy system. They have the fastest contraction speed but have a very low resistance to fatigue.

Fibre Type Modification

• Various types of exercises can bring about changes in the fibres in a skeletal muscle

• Endurance type exercises, such as running or swimming, cause a gradual transformation of type II B fibres into type II A fibres

• The transformed muscle fibres show a slight increase in diameter, mitochondria, blood capillaries, and strength

• A type 2A fibre can be changed to a type 2B fibres with training

• A type 1 cannot be change to type 2 fibre

Buccinator

• One of the first muscles that a human cancontrol

• Sucking reflex of a baby

• Smiling, chewing, and whistling

• Speech

Frontalis

• Change their facial expressions

• Allows the eyebrows to raise and the forehead to wrinkle

Masseter

• Chewing

• Strongest muscle in the human body

Orbicularis Oculi

• Important muscle in facial expression

• Close the eyelid, and to help in the passing and draining of tears

• Closes the eyelids gently in involuntary or reflex blinking

Orbicularis Oris

• Controls movements of the mouth and lips

• Kissing muscle

• Allows for facial expression

• Puckering the lips

• Forcefully exhale

• Closing the mouth

Temporalis

• Chewing

• Crushing and grinding objects between the molars

• Focal point for a recurring condition known as “tension headaches”

• Unclenching and clenching the jaw contracts this muscle

• Controls both retraction and elevation of the mandible

Zygomaticus

• Controls facial expression, drawing the mouth's angle upward and outward

• Causes the corners of a person's mouth to rise when they smile

• Cause dimples to form

Sternocleidomastoid

• Flexes the neck and helps with movement of the head

• Raises the sternum

• Helps the neck to turn to the side, flex to the side, and bend forward

Serratus Anterior

• Allows rotation of the arm and pulls the scapula forward and around the rib cage

• Also supports breathing

Trapezius

• Provides upright posture support

• Named for its trapezoid shape

• Used to tilt and turn the head and neck

• Shrug and steady the shoulders

• Twists the arms

• Elevates, depresses, rotates, and retracts the scapula

Diaphragm

• Inhalation

• Facilitates air to flow into the lungs

• Can become irritated (hiccups)

Intercostals

• Create and move the chest wall

• Assist with the breathing process

• Forced and quiet inhalation

External and Internal Oblique and Transverse Abdominus?

• Abdominal muscles

• Rotates the trunk

• Pulls the chest downwards to compresses the abdominal cavity

• Variety of trunk movements

Rectus Abdominus

• Flexes while doing crunches

• Used when a child is delivered

• Used during bowel movements

• Coughing

• Breathing in

• “six pack”

• Helps with jumping

Latissimus Dorsi

• Extending, adducting and rotating the arm

• Pull ups and chin ups

Erector Spinae

• Extend and laterally (side to side) bend the neck and trunk

• Grouping of 3 muscles

Pectoralis Major

• Control the movement of the arm

• Pull on the humerus to create lateral, vertical, or rotation

• Pushing

• Play a part in deep inhalation

Pectoralis Minor

• Depresses and stabilizes the scapula