The Significance of Physiological Processes in Animals

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  • 0:00 What Is Physiology?
  • 1:14 The Organ Systems
  • 5:53 Lesson Summary
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Lesson Transcript
Instructor: Jayne Yenko

Jayne has taught health/nutrition and education at the college level and has a master's degree in education.

Physiology is the study of how living organisms function. Looking at this through an organ-system view, we can see how animals evolved different ways of functioning for their particular habitats.

What Is Physiology?

Physiology is the study of how living organisms function, from cells all the way up to the whole organism and how organisms adapt to different environmental conditions in different habitats. We'll focus on organ-systems, which are collections of cells, tissues and organs that have specific functions within the bodies of organisms. These systems include the integumentary (or skin), musculoskeletal, cardiovascular/circulatory, immune, respiratory, digestive, urinary, reproductive and endocrine systems. All of these systems interact with each other, and their optimal functioning contributes to the health of the individual organism.

The basis of physiology is homeostasis, which is the state of dynamic consistency or maintenance of more or less stable conditions in the internal environment. Dynamic consistency means that physiological parameters, such as body temperature and blood pH, fluctuate around a set point. If any of the parameters were to move too far one way or the other, the organism wouldn't be able to survive. That means homeostasis is vital for survival of individual organisms.

The Organ Systems

Let's look at the organ systems and how they work in different animals.

Integumentary System

Skin is the protective barrier between the animal and the external environment. Small animals, like mice, have large skin areas compared to their total volume. They lose body heat easily and have difficulty keeping warm in winter. These animals tend to either stay active in winter or hibernate. On the other hand, elephants and other large animals have a small skin area in relation to their total volume and can find it difficult to stay cool. Their large ears act as fans to move air around their heads.

Musculoskeletal System

The musculoskeletal system supports and protects the animal and enables movement. The bones that make up the skeleton give structure to bodies and protect the brain. The ribs protect the heart and lungs and help in breathing. Muscles make up most of an animal's body and roughly half of its weight. Skeletal muscles work in pairs: when one contracts, the other relaxes. For example, when the biceps contract, the triceps relax, causing the human elbow to bend.

Cardiovascular System

The cardiovascular/circulatory system pushes the blood around the body with oxygen and nutrients for the cells and removes waste. This is especially important for homeostasis by maintaining stable pH levels and body temperature. In fish, blood passes through the heart once on its way to the gills and then around the rest of the body. In mammals and birds with lungs, blood passes through the heart twice, on its way to the lungs to pick up oxygen and then through the heart again to be pumped around the body.

Lymphatic System

The lymphatic or immune system is separate from the circulatory system, with its own fluid (lymph), vessels (lymphatic veins) and lymph nodes to filter out used cell parts, cancer cells and bacteria to keep the body healthy.

Respiratory System

The respiratory system utilizes the tiny alveoli in the lungs, which provide a large surface area to take in oxygen. Bird lungs act more like bellows, and oxygen is pumped through the lungs rather than changing in size and shape, like the lungs of mammals do. The evolution of this method of breathing for birds allows for very long migrations and flight at very high altitudes.

Digestive System

The digestive system processes water and nutrients for the body to use. Whatever food an animal eats has to be broken down into small molecules in order to pass into the bloodstream to be taken to the cells and used for energy.

Renal System

The urinary/renal system removes waste products. Animal bodies are made up of roughly 80% water, depending on the type of animal, age, sex and health. Generally, a loss of 15% of body water results in death. Animals lose water through their skin and lungs, feces and urine. To re-balance this water loss, animals must get water from their food and drink, and the water that is a byproduct of chemical reactions within the body.

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