Atlas of Human Anatomy

1. Head and Neck: Surface Anatomy and Skeletal Framework

The head and neck region is a complex area containing superficial structures, bones, ligaments, and vital organs.

Superficial and Deep Layers. The head and neck present a layered complexity, starting with superficial structures like facial muscles and progressing to deeper skeletal elements and vital organs. Understanding the surface anatomy is crucial for identifying underlying structures. For example, palpating the hyoid bone in the neck can help locate the larynx and trachea.

Skeletal Foundation. The skull and cervical vertebrae provide the bony framework for the head and neck. Ligaments connect these bones, providing stability and allowing for movement. Key structures include:

• The cranium, which protects the brain
• The facial bones, which define facial features
• The cervical vertebrae, which support the head and allow for neck movement

Clinical Significance. Knowledge of the skeletal framework is essential for diagnosing fractures, dislocations, and other injuries. For instance, understanding the location of the foramen magnum is critical in neurosurgery.

2. Back and Spinal Cord: Structure and Function

The back and spinal cord involve bones, ligaments, the spinal cord itself, muscles, and nerves.

Bony and Ligamentous Support. The vertebral column, composed of vertebrae and intervertebral discs, provides the primary support for the back. Ligaments reinforce the vertebral column, limiting excessive movement and preventing injury. The spinal cord, housed within the vertebral canal, is protected by these structures.

Muscles and Nerves. Muscles of the back are responsible for posture, movement, and stability. These muscles are innervated by spinal nerves, which also transmit sensory information from the back to the brain. Key muscle groups include:

• Erector spinae muscles, which extend the vertebral column
• Transversospinalis muscles, which rotate the vertebral column

Spinal Cord Function. The spinal cord serves as a conduit for neural signals between the brain and the rest of the body. It also contains neural circuits responsible for reflexes. Damage to the spinal cord can result in loss of motor and sensory function below the level of injury.

3. Thorax: Walls, Lungs, Heart, and Mediastinum

The thorax houses vital organs such as the lungs and heart, protected by the thoracic cage.

Thoracic Cage. The rib cage, formed by the ribs, sternum, and thoracic vertebrae, protects the lungs and heart. Intercostal muscles between the ribs facilitate breathing. The diaphragm, a large muscle at the base of the thorax, is the primary muscle of respiration.

Lungs and Pleura. The lungs are the organs of gas exchange, where oxygen is taken up and carbon dioxide is released. Each lung is surrounded by a pleural membrane, which reduces friction during breathing. Key features include:

• The lobes of the lungs (three on the right, two on the left)
• The bronchi, which carry air to and from the lungs

Heart and Mediastinum. The heart, located in the mediastinum (the central compartment of the thorax), pumps blood throughout the body. The mediastinum also contains the great vessels (aorta, vena cava, pulmonary artery), trachea, esophagus, and thymus. Understanding the spatial relationships of these structures is crucial for diagnosing and treating thoracic disorders.

4. Abdomen: Walls, Peritoneal Cavity, and Viscera

The abdomen contains the digestive organs and is lined by the peritoneum.

Abdominal Walls. The abdominal walls, composed of muscles and fascia, protect the abdominal organs. These muscles also play a role in posture, movement, and respiration. Key muscles include:

• Rectus abdominis
• External and internal obliques
• Transversus abdominis

Peritoneal Cavity. The peritoneal cavity is a space within the abdomen lined by the peritoneum, a serous membrane. The peritoneum supports and suspends the abdominal organs, allowing for movement and preventing adhesions. The peritoneal cavity contains:

• The greater and lesser omenta
• Mesenteries that suspend the intestines

Abdominal Viscera. The abdominal viscera include the digestive organs (stomach, small intestine, large intestine, liver, pancreas, gallbladder) and other structures (spleen, kidneys, adrenal glands). These organs perform essential functions such as digestion, absorption, and waste elimination. Knowledge of their location and relationships is crucial for diagnosing abdominal pain and other disorders.

5. Pelvis and Perineum: Bones, Muscles, and Organs

The pelvis and perineum contain the reproductive and urinary organs, supported by bones and muscles.

Pelvic Girdle. The pelvic girdle, formed by the hip bones and sacrum, provides support for the trunk and protects the pelvic organs. Ligaments connect these bones, providing stability and allowing for weight-bearing. The pelvic girdle also serves as an attachment point for muscles of the lower limb.

Pelvic Floor Muscles. The pelvic floor muscles support the pelvic organs and control urinary and fecal continence. These muscles are particularly important in women, as they support the uterus and vagina. Key muscles include:

• Levator ani
• Coccygeus

Pelvic Organs. The pelvic organs include the urinary bladder, rectum, and reproductive organs (uterus, ovaries, vagina in females; prostate gland, seminal vesicles, vas deferens in males). These organs perform essential functions such as urine storage, waste elimination, and reproduction. Understanding their anatomy is crucial for diagnosing and treating pelvic disorders.

6. Upper Limb: Shoulder, Arm, Forearm, and Hand

The upper limb allows for a wide range of movements, facilitated by muscles, nerves, and blood vessels.

Shoulder and Arm. The shoulder connects the upper limb to the trunk, allowing for a wide range of movements. The arm contains the humerus and muscles that flex and extend the elbow. Key structures include:

• The rotator cuff muscles, which stabilize the shoulder joint
• The biceps brachii and triceps brachii, which flex and extend the elbow

Forearm and Hand. The forearm contains the radius and ulna, which allow for pronation and supination. The hand contains the carpal, metacarpal, and phalangeal bones, which allow for fine motor movements. Key structures include:

• The flexor and extensor muscles of the wrist and fingers
• The median, ulnar, and radial nerves, which innervate the hand

Neurovascular Supply. Nerves and blood vessels run along the upper limb, providing innervation and blood supply to the muscles and skin. Damage to these structures can result in loss of motor and sensory function. For example, compression of the median nerve in the carpal tunnel can cause carpal tunnel syndrome.

7. Lower Limb: Skin, Muscles, Bones, and Joints

The lower limb is specialized for weight-bearing and locomotion.

Skin and Superficial Anatomy. The skin of the lower limb varies in thickness and texture depending on the region. Superficial veins and nerves are located just beneath the skin. Understanding the surface anatomy is crucial for identifying underlying structures.

Muscles and Movement. Muscles of the lower limb are responsible for hip, knee, and ankle movements. These muscles are organized into compartments, each with a specific function. Key muscle groups include:

• The gluteal muscles, which extend and abduct the hip
• The quadriceps femoris, which extends the knee
• The hamstring muscles, which flex the knee

Skeletal Framework. The femur, tibia, and fibula provide the bony framework for the lower limb. The hip, knee, and ankle joints allow for movement and weight-bearing. Understanding the skeletal anatomy is crucial for diagnosing fractures, dislocations, and other injuries.

Last updated: April 21, 2025