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Questions and Answers
Which type of joint permits flexion and extension around the transverse axis?
What structure reduces friction between articular surfaces in synovial joints?
Which of the following types of joints is classified as uniaxial, allowing rotation?
What is the primary function of ligaments in synovial joints?
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Which accessory feature of synovial joints helps to eliminate irregularities between articular surfaces?
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Which of the following is NOT a type of synovial joint?
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What is the role of the articular capsule in synovial joints?
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Which joint type is characterized by having a fibrocartilaginous ring that deepens the articular surface?
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What is the primary function of bones in the musculoskeletal system?
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Which part of the skeleton consists of the skull, vertebrae, ribs, and sternum?
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What type of bones contains air cells or sinuses?
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Which of the following is not a class of joints based on their movement capability?
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What type of bone is characterized by having a shaft and two ends?
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What is the outer layer covering all bones, except their joint surfaces, called?
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How many bones are typically found in a human adult skeleton?
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Which component of the bone is responsible for blood cell production?
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What classification of joints are sutures of the skull categorized under?
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Which surface feature on bones is a rounded articular area?
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Which type of joint allows for flexion, extension, abduction, and adduction?
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What is the shape of the articular surfaces in condyloid joints?
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What type of muscle is responsible for heart contractions?
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Which part of a skeletal muscle is the fleshy part known as?
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Which feature does NOT contribute to joint stability?
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What is the definition of isotonic contraction?
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Which joint type involves gliding or sliding movements?
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What does Hilton's law refer to?
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Which of the following is NOT a characteristic of smooth muscle?
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What is a motor unit composed of?
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Study Notes
Introduction to the Musculoskeletal System
- The musculoskeletal system is composed of passive structures (bones and joints) and active structures (muscles).
Bones
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Bones are a rigid form of connective tissue, constituting the body’s skeleton.
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They are the second hardest structure in the body, after tooth enamel.
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They comprise approximately 15% of the total body weight.
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Key functions of bones:
- Provide a framework for the body.
- Serve as insertion points for muscles.
- Store calcium and phosphorus.
- Protect vital organs.
- Produce blood cells.
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Bones are living tissues with a blood and nerve supply.
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All bones are covered with a layer called the periosteum, except their joint surfaces.
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Bones possess a degree of elasticity due to organic substances and significant rigidity provided by inorganic substances, mainly calcium phosphate.
Internal Structure of a Bone
- Bones consist of compact bone, spongy (cancellous) bone, and bone marrow.
- Bone marrow is found within the medullary cavity and exists in two forms:
- Red bone marrow, responsible for blood cell production.
- Yellow bone marrow, primarily composed of fat.
- Nutrient foramina and nutrient arteries supply the bone with blood.
The Skeleton
- The adult human skeleton comprises 206 bones.
- It provides structure and support for soft tissues.
- It is divided into two main parts:
- The axial skeleton, which forms the central core of the body:
- Skull (22 bones).
- Vertebral column (26 bones).
- Ribs (25 bones).
- Sternum (1 bone).
- The appendicular skeleton, which comprises the bones of the upper and lower limbs:
- Upper limbs (64 bones).
- Lower limbs (62 bones).
- The axial skeleton, which forms the central core of the body:
- Auditory bones (in the middle ear) add six bones to the total count.
Different Types of Bones
- Bones are classified into different types based on their shape and structure:
- Long bones: Characterized by a shaft (diaphysis) and two ends (epiphyses).
- Short bones: Roughly cuboidal in shape.
- Flat bones: Thin, flat, and often curved.
- Irregular bones: Have an irregular shape.
- Pneumatic bones: Contain air cells or sinuses.
- Sesamoid bones: Found within tendons.
- Accessory bones: Develop as a result of additional ossification centers or incomplete fusion of bones.
Surface Features of Bones
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Bone surfaces are not smooth; they display various elevations, depressions, and holes.
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These features have specific names:
- Linear elevations:
- Line (a narrow ridge).
- Crest (a prominent ridge).
- Round elevations:
- Tubercle (a small eminence).
- Protuberance (a swelling).
- Sharp elevations:
- Spine (a pointed projection).
- Process (any projection from a bone).
- Rounded articular areas:
- Head (a prominent rounded articular end).
- Condyle (a rounded articular projection).
- Openings:
- Foramen (a hole).
- Fissure (a narrow cleft).
- Aperture (an opening).
- Canal: A foramen with length.
- Meatus: A canal leading into a structure.
- Facets: Smooth, flat articular surfaces for joint formation.
- Depressions:
- Fossa (a small depression).
- Groove (sulcus), a long narrow depression.
- Linear elevations:
Joints
- Arthrology is the study of joints.
- Joints are formed by the articulation of two or more bones.
- The articular system consists of joints, associated bones, and ligaments.
Classification of Joints
- Joints are categorized based on the degree of movement they allow:
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Fibrous joints (fixed):
- Sutures: Found only in the skull.
- Gomphosis: Between teeth and jaws.
- Syndesmosis: Articulating surfaces connected by strong connective tissue.
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Cartilaginous joints (slightly moveable):
- Symphysis: Connected by a fibrocartilage disc between articular surfaces (e.g., pubic symphysis).
- Synchondrosis: Connected by hyaline cartilage between articular surfaces (e.g., sphenoid-occipital joint).
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Synovial joints (freely moveable):
- Hinge joints: Allow flexion and extension around a transverse axis (e.g., elbow joint).
- Bicondylar joints: Allow flexion/extension and some rotation around a transverse axis (e.g., knee joint).
- Pivot joints: Allow rotation around a vertical axis (e.g., radioulnar joints).
- Saddle joints: Allow flexion/extension and abduction/adduction around two axes (e.g., carpometacarpal joint of the thumb).
- Condyloid joints: Allow flexion/extension and abduction/adduction around two axes (e.g., radiocarpal joint, metacarpophalangeal joints).
- Ball-and-socket joints: Allow movement in multiple planes (e.g., shoulder joint).
- Plane joints: Allow gliding or sliding movements (e.g., intercarpal joints).
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Fibrous joints (fixed):
Synovial Joints
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Synovial joints share common features:
- Articular (joint) cavity: A space between the articular surfaces.
- Articular cartilage: Covers the articular surfaces, reducing friction.
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Articular capsule: A capsule surrounding the joint, composed of two layers:
- Fibrous membrane: Provides protection and stability.
- Synovial membrane: Lines the fibrous membrane, secreting synovial fluid for lubrication.
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Synovial joints may have accessory features:
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Ligaments: Strong connective tissue that connects articulating bones, limiting excessive joint movement.
- Intrinsic ligaments: Part of the articular capsule.
- Extrinsic ligaments: Separate from the articular capsule.
- Articular disc: A disc of fibrocartilage that eliminates irregularities between articular surfaces.
- Labrum: A fibrocartilaginous ring that deepens the articular surface in specific joints.
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Ligaments: Strong connective tissue that connects articulating bones, limiting excessive joint movement.
Nerves and Vessels of Joints
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Nerve Supply of Joints:
- Hilton’s Law: The nerves supplying a joint are branches of the nerves that innervate the muscles acting on the joint and the nerves innervating the sensory areas surrounding the joint.
- Nerves convey impulses related to conscious proprioception (from the joint capsule) and pain (from the fibrous membrane).
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Vessel Supply of Joints:
- Numerous vessels contribute to the blood supply of a joint, branching from nearby vessels.
Features Supporting Joint Stability
- The stability of a joint, preventing dislocation, relies on several factors:
- Negative pressure within the joint cavity.
- Joint capsule and ligaments.
- Muscles and their tendons surrounding the joint.
- Shapes of the articular surfaces.
Muscles
- Muscles are classified into three types:
- Skeletal (voluntary) muscles: Mostly allow voluntary movement (with some exceptions).
- Smooth (involuntary) muscles: Movement controlled internally.
- Cardiac (involuntary) muscle: Found only in the heart.
Parts of a Skeletal Muscle and Related Terms
- A skeletal muscle consists of:
- Belly (fleshy part): The main body of the muscle.
- Tendon (or aponeurosis): A strong fibrous cord that attaches the muscle to bones, cartilages, skin, or fascia.
- Origin: The more fixed attachment point of the muscle.
- Insertion: The more movable attachment point of the muscle.
Fascial System
- The fascial system consists of two main layers:
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Superficial fascia: A subcutaneous layer consisting of two parts:
- Superficial layer: A layer of loose connective tissue containing fat.
- Deep layer: Dense, membranous layer.
- Deep fascia: A dense connective tissue sheet that surrounds muscles and organs, providing support and compartmentalization.
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Superficial fascia: A subcutaneous layer consisting of two parts:
Muscle Terminology
- Muscle names are based on various characteristics, including:
- Shape: (e.g., deltoid, quadratus)
- Size: (e.g., major, minor)
- Number of heads or bellies: (e.g., biceps, triceps)
- Depth: (e.g., superficial, internal)
- Attachment: (e.g., coracobrachialis, brachioradialis)
- Position: (e.g., brachii, dorsi, pectoralis)
- Action: (e.g., extensor, levator)
Muscle Contraction
- Contraction shortens a muscle by approximately 1/3 or 1/2.
- Two types of muscle contraction:
- Isotonic contraction: The muscle length decreases.
- Isometric contraction: The muscle length remains unchanged.
Innervation of Muscles
- The smallest functional unit of muscle innervation is a motor unit.
- A motor unit consists of a motor neuron and all the muscle fibers it innervates.
- A single motor neuron can innervate thousands of muscle fibers. In some muscles, a motor neuron might innervate a smaller number of fibers (e.g., muscles involved in fine motor control).
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Description
This quiz explores the key aspects of the musculoskeletal system, focusing on bones, their structure, and function. It covers the roles bones play in the body, their composition, and their vital functions. Perfect for students studying anatomy and physiology.
