Heart

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💖 UNIT: HEART (Anatomy)

Cardiovascular System – BSc Nursing

1. Definition

The heart is a hollow, muscular organ that acts as a pump to circulate blood throughout the body.

2. Location

  • Situated in the middle mediastinum of the thorax
  • Between the two lungs
  • Immediately above the diaphragm
  • Lies behind the sternum and adjoining costal cartilages
  • Mostly to the left of the midline

3. Size and Weight

  • Size: Slightly larger than a clenched fist
  • Average Weight:
    • Male: ~300 g
    • Female: ~250 g

4. Coverings and Wall Layers of the Heart

The heart wall consists of three layers:

  1. Epicardium

    • Outermost layer
    • Protective covering

  2. Myocardium

    • Middle and thickest layer
    • Composed of cardiac muscle
    • Responsible for pumping action

  3. Endocardium

    • Innermost layer
    • Lines the chambers and valves

5. Anatomical Position of the Heart

Apex

  • Directed downward, forward, and to the left
  • Located in the 5th intercostal space
  • Just medial to the mid-clavicular line
  • Approximately 9 cm from the midline

Base

  • Directed upward and backward
  • Lies on the right side
  • Extends up to the right 3rd costal cartilage

6. Borders of the Heart

  • Right border
  • Left border
  • Superior border
  • Inferior border

7. Surfaces of the Heart

  • Sternocostal (anterior) surface
  • Diaphragmatic (inferior) surface
  • Pulmonary surface

8. Chambers of the Heart

The heart has four chambers:

  • Two atria – receiving chambers
  • Two ventricles – pumping chambers

Chambers and Functions

Chamber Receives Blood From Type of Blood Function
Right Atrium SVC, IVC, Coronary sinus Deoxygenated Receives blood from body
Right Ventricle Right atrium Deoxygenated Pumps blood to lungs
Left Atrium 4 pulmonary veins Oxygenated Receives blood from lungs
Left Ventricle Left atrium Oxygenated Pumps blood to whole body

Note:

  • Left ventricle has the thickest wall because it pumps blood to the entire body.

9. External and Internal Features

External Features

  • Interventricular sulcus – separates right and left ventricles
  • Coronary sulcus (atrioventricular groove) – separates atria from ventricles

Internal Features

  • Sinus venarum – smooth posterior part of right atrium
  • Crista terminalis – muscular ridge separating sinus venarum
  • Auricle – ear-shaped pouch in atria
  • Sinoatrial (SA) node – pacemaker of the heart

10. Course of Blood Circulation

A. Pulmonary Circulation

Purpose: Oxygenation of blood

Pathway:

  1. Right ventricle
  2. Pulmonary trunk
  3. Pulmonary arteries
  4. Lung capillaries (gas exchange)
  5. Pulmonary veins
  6. Left atrium

B. Systemic Circulation

Purpose: Supply oxygen to the body

Pathway:

  1. Left atrium
  2. Left ventricle
  3. Aorta
  4. Arteries → capillaries (tissue exchange)
  5. Veins
  6. Superior & Inferior vena cava
  7. Right atrium

✨ Key Exam Tips

  • Always draw a neat diagram of the heart in exams
  • Write definitions first
  • Use headings and tables
  • Mention functions clearly
  • Highlight left ventricle thickness and SA node


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