The heart and lungs are major organs of the human body. Use the level of cell organization as a guide to differentiate between the major tissues, cell types, and organelles that are contained within each of these organs as well as which organ system each is part of.  

The heart is composed of mostly cardiac muscle tissue, which contains smooth muscle cells, fibroblasts, and cardiomyocytes. The lungs contain mostly epithelial cells.

Expert Answers

An illustration of the letter 'A' in a speech bubbles

The five levels of cell organization are 1.) the cell itself, 2.) the tissue made up by the cells, 3.) the organ made up by the tissues, 4.) the body system the organ belongs to, and 5.) the entire organism. The heart is part of the cardiovascular system, and the lungs belong to the respiratory system. These two organs (and systems) are very closely linked, because both play an important role in gas exchange.

Most cells that make up lung tissue are epithelial cells, which secrete mucus; however, there are also structural cells and nerve cells present. If you specifically look at alveolar tissue, the main cell types are macrophages (immune cells) and pneumocytes (epithelial cells). Pneumocytes can be squamous or cuboidal. Gas exchange occurs across the alveolar membrane, as CO2 diffuses out of the bloodstream and O2 diffuses into it.

Meanwhile, the heart is composed of mostly cardiac muscle tissue. At the cellular level, this type of tissue is composed of smooth muscle cells, fibroblasts (connective tissue cells), and cardiomyocytes (cells that contract the heart).

In terms of organelles, most cells are fairly similar. They have a nucleus for storing genetic information, ribosomes (located on the endoplasmic reticulum) to produce proteins and a Golgi apparatus to package them, mitochondria to create ATP, and lysosomes to break down waste and toxins.

Not every cell type will have all of these organelles, depending on what its function is—for example, red blood cells lack a nucleus, because they need to be small enough to fit through capillaries and reach other cells in the body. However, for the most part, cells require these organelles so that they can function the way they are supposed to.

Last Updated by eNotes Editorial on October 1, 2020
Soaring plane image

We’ll help your grades soar

Start your 48-hour free trial and unlock all the summaries, Q&A, and analyses you need to get better grades now.

  • 30,000+ book summaries
  • 20% study tools discount
  • Ad-free content
  • PDF downloads
  • 300,000+ answers
  • 5-star customer support
Start your 48-Hour Free Trial