Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

7. The Skeletal System

The Pectoral Girdle

Anatomy & Physiology

7. The Skeletal System

The Pectoral Girdle

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3:07 minutes

Problem 22

Textbook Question

At work, a box fell from a shelf onto Ella's acromial region. In the emergency room, the physician felt that the head of her humerus had moved into the axilla. What had happened to Ella?

Verified step by step guidance

Step 1: Understand the anatomical terms mentioned in the problem. The 'acromial region' refers to the area near the acromion, which is the bony prominence on the scapula (shoulder blade). The 'axilla' refers to the armpit region. The 'head of the humerus' is the rounded top part of the upper arm bone that fits into the shoulder joint.

Step 2: Recognize the injury described. The head of the humerus moving into the axilla suggests a dislocation of the shoulder joint. Specifically, this is likely an anterior or inferior dislocation, where the humeral head moves out of its normal position in the glenoid cavity of the scapula.

Step 3: Explain the mechanism of injury. A box falling onto the acromial region could have exerted force on the shoulder joint, potentially causing the humeral head to be displaced. This type of injury often occurs when there is a combination of forceful impact and improper positioning of the arm.

Step 4: Discuss the implications of the injury. A shoulder dislocation can damage surrounding structures, such as ligaments, tendons, and nerves. The physician would need to assess for additional injuries, such as nerve compression or tearing of the rotator cuff muscles.

Step 5: Outline the typical treatment process. The physician would likely perform a physical examination and imaging studies (e.g., X-rays) to confirm the dislocation. Treatment typically involves reducing the dislocation (manually repositioning the humeral head into the glenoid cavity), followed by immobilization and physical therapy to restore function and prevent recurrence.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acromial Region

The acromial region refers to the area of the shoulder where the acromion, a bony projection of the scapula, is located. This region is crucial for shoulder stability and movement, and injuries here can affect the surrounding muscles and joints. Understanding the anatomy of the acromial region helps in diagnosing shoulder injuries.

Humeral Head Dislocation

A humeral head dislocation occurs when the head of the humerus, the upper arm bone, is displaced from its normal position in the shoulder joint. This can happen due to trauma, such as a fall or impact, leading to severe pain, immobility, and potential damage to surrounding nerves and blood vessels. Recognizing the signs of dislocation is essential for prompt treatment.

Axilla

The axilla, commonly known as the armpit, is the area beneath the shoulder joint that contains important structures such as blood vessels, nerves, and lymph nodes. It serves as a passageway for nerves and blood vessels to the arm. Understanding the anatomy of the axilla is vital in assessing injuries related to shoulder dislocations, as the humeral head may move into this space during a dislocation.

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Textbook Question

Which of the following is primarily responsible for stabilizing, positioning, and bracing the pectoral girdle?

(a) Tendons

(b) Ligaments

(d) Muscles

(e) The shape of the bones within the joint

Name the bones of the shoulder girdle.

Why would a self-defense instructor advise a student to strike an attacker’s clavicle?

While fireman Fred is fighting a fire in a building, part of the ceiling collapses, and a beam strikes him on his left shoulder. He is rescued, but has a great deal of pain in his shoulder. He cannot move his arm properly, especially in the anterior direction. His clavicle is not broken, and his humerus is intact. What is the probable nature of Fred’s injury?

In anatomical position, the ulna lies:

(a) Medial to the radius

(b) Lateral to the radius

(d) Superior to the radius