Human Skeletal System Overview

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Questions and Answers

What is the primary role of the myosin heads in muscle contraction?

To polymerize G actin into F actin

To link thick and thin filaments (correct)

To stabilize actin filaments

To form the sarcomere structure

Which component of muscle fibers corresponds to the structural units of contraction?

Sarcoplasmic reticulum

Myofibrils

Sarcomeres (correct)

Mitochondria

Which statement accurately describes the role of tropomyosin in muscle contraction?

It polymerizes to form actin filaments

It activates ATPase activity in myosin

It directly forms cross bridges with myosin

It stabilizes actin filaments by covering active sites (correct)

During muscle contraction, which region of the sarcomere decreases in size?

H Zone Signup and view all the answers

Which type of muscle fiber is primarily responsible for powerful, short-duration contractions?

Fast-twitch fibers Signup and view all the answers

What is the main weight bearing component of a typical vertebra?

Vertebral body Signup and view all the answers

Which part of the vertebrae forms the lateral and posterior walls of the vertebral canal?

Vertebral arch Signup and view all the answers

What characterizes thoracic vertebrae specifically?

They have large costal elements for articulation Signup and view all the answers

How many bones comprise the human skull?

22 bones Signup and view all the answers

Which bone is part of the facial structure of the skull?

Mandible Signup and view all the answers

What is the primary function of the vertebral arch?

Protection of spinal cord Signup and view all the answers

Which bones are considered cranial bones of the human skull?

Parietal, occipital, and temporal Signup and view all the answers

Which bone is NOT a cranial bone?

Mandible Signup and view all the answers

What is the defining characteristic of osteoporosis?

Bone loss greater than bone growth Signup and view all the answers

Which of the following bones is least likely affected by osteoporosis?

Skull Signup and view all the answers

What is a common visible effect of osteoporosis in elderly individuals?

Curved back from compression fractures Signup and view all the answers

Which group has the highest risk of developing osteoporosis?

Women over 50 Signup and view all the answers

What type of muscle is responsible for the movement of food along the gastrointestinal tract?

Smooth muscle Signup and view all the answers

What role does skeletal muscle play in body posture?

Requires continual adjustment of muscles Signup and view all the answers

How does cardiac muscle contribute to body function?

Pumps blood throughout the body Signup and view all the answers

What is a potential consequence of osteoporotic bone changes?

Progressively weakened bones Signup and view all the answers

Which type of muscle is classified as voluntary?

Skeletal muscle Signup and view all the answers

Which factor does NOT increase the risk of osteoporosis?

Higher levels of physical activity Signup and view all the answers

How many bones make up the pectoral girdle?

4 Signup and view all the answers

What is the primary function of the pectoral girdle?

Anchoring limbs to the axial skeleton Signup and view all the answers

Which of the following statements about the pectoral girdle is true?

It is not typically weight-bearing. Signup and view all the answers

What characteristic of the glenoid cavity contributes to the mobility of the shoulder joint?

It is shallow and loose. Signup and view all the answers

What is the consistency of synovial fluid compared to?

Egg white Signup and view all the answers

Which movement is primarily allowed by a hinge joint?

Flexion and extension Signup and view all the answers

Which feature of the shoulder joint increases its susceptibility to dislocation?

The loose joint capsule. Signup and view all the answers

What is the total number of bones in the upper limb?

64 Signup and view all the answers

Which type of synovial joint allows for the greatest range of movement?

Ball & socket Signup and view all the answers

Which bones make up the upper limb?

Scapulae and clavicles Signup and view all the answers

In which joint type would you find gliding or sliding movements?

Plane Signup and view all the answers

What is the primary function of articular cartilage in synovial joints?

To reduce friction Signup and view all the answers

Which bone is NOT part of the pelvic girdle?

Clavicle Signup and view all the answers

What is the total number of bones in the lower limb?

62 Signup and view all the answers

Which type of joint allows for both rotation and a limited range of movement between two bones?

Pivot Signup and view all the answers

Which aspect of the shoulder joint allows for great maneuverability?

The ball-and-socket structure. Signup and view all the answers

Which synovial joint type consists of concave and convex joint surfaces?

Saddle Signup and view all the answers

What type of joint connects the elbow and allows for flexion and extension?

Hinge Signup and view all the answers

Which of the following describes a synovial joint's structure?

Composed of bony surfaces covered with articular cartilage Signup and view all the answers

Which joint type permits movements like flexion, extension, abduction, adduction, and circumduction?

Condyloid Signup and view all the answers

Study Notes

Vertebrae

Vertebral body is the main weight-bearing component of the vertebrae
Vertebral arch forms the lateral and posterior walls of the vertebral canal
Vertebral arch also serves as the point of attachment for muscles and ligaments, as well as site of articulation with adjacent vertebrae
Contains the spinal cord, blood vessels and connective tissue
Thoracic vertebrae - large costal elements form articulation

Vertebral Column

Vertebrae increase in size from C2 to L5

Human Skull

Consists of 22 bones: 8 cranial and 14 facial (+6 inner ear ossicles)
Bones are joined immovably, except the mandible
Divided into: forehead - frontal, roof - parietal, side - temporal, back - occipital

Appendicular Skeleton

Consists of the bones of the pectoral and pelvic girdles and the upper and lower limbs
Upper limb: 64 bones; pectoral girdle: scapulae and clavicles (4); arms and forearms (6); wrist and hands (54)
Lower limb: 62 bones; pelvic girdle (2), thigh and lower leg (8); ankle and feet (52)

Pectoral (Shoulder) Girdle

Anchors limbs to the axial skeleton
Consists of 2 clavicles and 2 scapulae
Not typically weight bearing, stability is sacrificed for mobility
Most mobile joint in the body, hence not very stable and can easily dislocate the shoulder

Synovial Joints

Most mobile joint in the body - why? - The head of the humerus rests in the glenoid cavity of the scapula, which is shallow and the joint capsule is loose.
Provides great manoeuvrability but can be easily dislocated

General Structure of Synovial Joints

Joint Cavity: contains synovial fluid
Articular Cartilage: reduces friction between joints
Synovial Fluid: egg white consistency, lubricates joints, preventing damage

Types of Synovial Joints

Pivot: allows rotation, round bony process fits into bony ligamentous socket
Hinge: Permits flexion and extension only, e.g., elbow
Saddle: concave and convex joint surfaces
Plane: permits gliding or sliding movements
Condyloid: permits flexion, extension, abduction, adduction, and circumduction, e.g., wrist
Ball & Socket: allows for movement in several axes, rounded head, e.g., hip

Osteoporosis

Bone mineral density is reduced
Bone loss is greater than bone growth
Bones progressively weaken and fracture with minor stress
Most common bones affected: neck of femur, wrist, forearm, hip and vertebrae
No obvious symptoms until fractures
Higher risk groups: elderly, women over 50, family history, petit and thin, previous fracture, Caucasian and Asian women, certain diseases, and lifestyle factors

Muscle

Specialised for generating force and motion
Represents ~50% body mass in adult humans
Divided into three types: skeletal, cardiac and smooth muscle
Many similarities but also differ considerably from one another

Muscle Functions

Body Movement: skeletal muscle contraction
Body Posture: continual adjustment of skeletal muscles
Support and Protection: skeletal muscles surrounding joints and within the abdominal wall
Sphincter Control: skeletal and smooth muscle e.g., cardiac sphincter in stomach, bladder, and anus
Movement of food along GI tract: smooth muscle generates peristalsis
Regulation of Blood: Cardiac muscle pumps blood

Muscle Histology

Skeletal Muscle Cell:
- Cell membrane - sarcolemma
- Cytoplasm - sarcoplasm
- Full of myofibrils
- Myofibrils - actin/myosin
- Many mitochondria
- Extensive endoplasmic reticulum - sarcoplasmic reticulum

Muscle Fibre Anatomy

Muscle Fibre: Contains myofilaments
Myofilaments: contractile units called sarcomeres
Sarcomere: Striations caused by overlapping actin and myosin (myofilaments)

Muscle Cell Function: Contraction

Actin and Myosin make up - 90% muscle protein
Actin: Actin subunits polymerise into long filamentous or “F actin” and two intertwined actin filaments
Myosin: Rod-like tail attached to two globular heads, tail - intertwines helices. Globular heads link thick and thin filaments in contraction.

Sarcomere Contraction

Sliding Filament Theory
Actin filaments slide past myosin filaments, shortening the sarcomere

Sarcomere Components

A band: dark band containing myosin filaments
I band: light band containing actin filaments
H zone: central region of A band containing only myosin filaments
M line: middle of sarcomere
Z disc: attachment point for actin filaments.

Muscular System

Muscles can be classified into three functional groups:
- Agonist: the prime mover - responsible for the primary movement
- Antagonist: may stretch or be relaxed - works opposite to the agonist
- Synergist: may add extra force or prevent undesirable effects - assists the agonist
- Fixator: maintains body structure, e.g., stabilising a joint

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Description

This quiz covers key aspects of the human skeletal system, including the vertebrae, vertebral column, human skull, and appendicular skeleton. You'll learn about the structure and function of bones, as well as their arrangement in various parts of the body. Test your knowledge of human anatomy with this engaging quiz!