Anatomy & Physiology Study Guide: Bones, Joints, Muscles, and Nervous Tissue

Bones of the Upper Limb and Shoulder

Scapula Anatomy

The scapula, or shoulder blade, is a flat, triangular bone that forms the posterior part of the shoulder girdle. It serves as an attachment site for several muscles and articulates with the humerus and clavicle.

• Key Landmarks:

  • Spine: A prominent ridge running across the posterior surface.

  • Acromion: The lateral extension of the spine, articulates with the clavicle.

  • Coracoid process: A hook-like projection on the anterior surface.

  • Glenoid cavity: A shallow socket that articulates with the head of the humerus.

  • Suprascapular notch: A notch on the superior border for nerve passage.

  • Borders: Superior, medial (vertebral), and lateral (axillary).

  • Angles: Superior, inferior, and lateral.

  • Fossae: Subscapular (anterior), supraspinous and infraspinous (posterior).

• Example: The acromion is palpable at the top of the shoulder and is a common site for muscle attachment.

Bones of the Hand

The human hand consists of several bones organized into phalanges, metacarpals, and carpals. Proper identification of these bones is essential for understanding hand anatomy and function.

• Phalanges: The fingers contain distal, middle, and proximal phalanges (except the thumb, which has only distal and proximal).

• Metacarpals: Five metacarpal bones form the palm, numbered I-V from thumb to little finger.

• Carpals: Eight carpal bones form the wrist.

• Ulnar styloid process: A bony prominence on the distal end of the ulna, palpable on the medial side of the wrist.

• Example: In anatomical diagrams, the thumb is always lateral in the standard anatomical position.

Label	Bone
A	Distal phalanx V
B	Proximal phalanx V
C	Metacarpal V
D	Distal phalanx I
E	Metacarpal I

Bones of the Pelvis

Coxal Bone Views and Landmarks

The coxal bone (hip bone) is a large, irregular bone forming the lateral part of the pelvis. It consists of three fused bones: ilium, ischium, and pubis.

• Medial View: Shows the inner surface, including the iliac fossa and sacroiliac joint.

• Lateral View: Shows the acetabulum, where the femur articulates.

• Key Markings: The sacrum articulates with the coxal bone at the sacroiliac joint.

• Example: The acetabulum is the cup-shaped cavity that receives the head of the femur.

Number	View
1	Medial view of the left coxal bone
2	Lateral view of the left coxal bone
3	Medial view of the right coxal bone

Joints and Their Classification

Types of Joints

Joints, or articulations, are connections between bones that allow for movement and provide stability. They are classified based on their structure and degree of movement.

• Synchondrosis: A type of cartilaginous joint where bones are joined by hyaline cartilage. These joints are typically immovable (synarthrosis).

• Synovial Joints: Freely movable joints characterized by a synovial cavity filled with fluid.

• Example: The epiphyseal plate in growing bones is a synchondrosis; the knee is a synovial joint.

Joint Type	Movability
Synchondrosis	Immovable (synarthrosis)
Synovial	Freely movable (diarthrosis)

Synovial Joint Structure

Synovial joints are the most common and movable type of joint in the body. They have a complex structure that allows for a wide range of motion.

• Articular cartilage: Covers the ends of bones, reducing friction and absorbing shock.

• Synovial membrane: Lines the joint capsule and secretes synovial fluid.

• Fibrous layer: Provides strength and stability to the joint capsule.

• Ligaments: Bands of connective tissue that stabilize the joint.

• Example: The shoulder and knee joints are synovial joints.

Knee Joint Anatomy

The knee joint is a complex synovial joint that includes several important structures for stability and movement.

• FCL (Fibular Collateral Ligament): Provides lateral stability.

• ACL (Anterior Cruciate Ligament): Prevents anterior displacement of the tibia.

• PCL (Posterior Cruciate Ligament): Prevents posterior displacement of the tibia.

• Menisci: Crescent-shaped cartilage that cushions and stabilizes the joint.

• Example: Injury to the ACL is common in athletes and can cause knee instability.

Muscle Tissue Structure

Connective Tissue Layers of Muscle

Skeletal muscle is organized into bundles surrounded by connective tissue layers that provide support and transmit force.

• Endomysium: Thin connective tissue surrounding individual muscle fibers.

• Perimysium: Connective tissue that surrounds groups of muscle fibers, forming fascicles.

• Epimysium: Dense connective tissue that surrounds the entire muscle.

• Example: The perimysium holds muscle fascicles together.

Layer	Location
Endomysium	Surrounds individual muscle fibers
Perimysium	Surrounds fascicles (bundles of fibers)
Epimysium	Surrounds entire muscle

Sarcomere Structure and Function

The sarcomere is the basic contractile unit of muscle fiber, composed of organized thick and thin filaments.

• Thick filaments: Made of myosin.

• Thin filaments: Made of actin, troponin, and tropomyosin.

• Key regions: A band (length of thick filaments), I band (thin filaments only), H zone (center of A band, thick filaments only), M line (center of sarcomere), Z disc (boundary between sarcomeres).

• During contraction: The A band remains unchanged, while the I band and H zone decrease in width.

• Example: Muscle contraction is driven by the sliding filament mechanism.

Region	Changes During Contraction?
A band	No
I band	Yes
H zone	Yes

Nervous Tissue: Myelination

Myelinated vs. Unmyelinated Axons

Axons in the nervous system may be myelinated or unmyelinated, affecting the speed and efficiency of nerve impulse transmission.

• Myelin sheath: An insulating layer formed by Schwann cells (PNS) or oligodendrocytes (CNS), composed of proteins and fatty substances.

• Function: Increases the speed of electrical impulse conduction via saltatory conduction.

• Unmyelinated axons: Conduct impulses more slowly because the action potential must propagate along the entire membrane.

• Example: Loss of myelin sheaths, as in multiple sclerosis, can cause symptoms such as vision loss, numbness, weakness, or paralysis.

White Matter in the CNS

White matter in the central nervous system appears white due to the high concentration of myelinated axons.

• Function: Transmits signals rapidly between different regions of the brain and spinal cord.

• Example: The corpus callosum is a major white matter tract connecting the two cerebral hemispheres.

Key Equations

• Sliding Filament Theory: $\text{Muscle contraction force} \propto \text{number of cross-bridges formed}$

• Nerve Conduction Velocity: $v = \sqrt{\frac{d}{R_m C_m}}$ where $v$ is conduction velocity, $d$ is axon diameter, $R_m$ is membrane resistance, $C_m$ is membrane capacitance

Additional info: Some content and terminology were inferred and expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.