Animal Organs & Systems Biology Lesson # 6 Animal Organs & Systems

Tissues & Organs Recall that there are four animal tissues: epithelial, connective, muscle, and nervous tissue. Most organs are made up of all four tissues. There are too many organs to discuss in one lesson, but we will focus on a few important ones in the human body. Biologists categorize organ systems according to their main functions, and there are 11 main organ systems in the human body. We will only focus on five.

The Respiratory System The main function of this system is gas exchange – oxygen is inhaled and carbon dioxide is released – the site of gas exchange is in the alveoli. The main organ involved: the lungs

Respiratory Air Passage: mouth/nose pharynx  trachea  bronchi  bronchioles  alveoli  capillaries Air enters the mouth or nose and travels into the pharynx (back of mouth/throat) trachea (also called the windpipe) – flexible tube made of cartilage rings (connective tissue) bronchi (tubes, there are 2 of them, one for each lung) into smaller tubes called bronchioles finally into smaller sacs called alveoli (made of epithelial tissue) alveoli are surrounded by thin blood vessels called capillaries that allow O2 to enter the capillaries into the blood to travel throughout the body, and allow CO2 to travel from the capillaries back to the alveoli and out the same way it came through the mouth or nose.

Lungs

The Circulatory System The main function of this system is to transport blood throughout the body. The main organ involved: the heart Arteries are thick-walled vessels that carry blood away from the heart, with a strong pressure that pushes the blood along Veins carry blood back to the heart, and are thinner and lower in pressure. They also contain valves to ensure blood does not flow backwards.

Capillaries & Diffusion Capillaries connect the veins and arteries, and are the smallest blood vessels – about one cell thick. Oxygen and carbon dioxide flow in and out of capillaries by diffusion (the movement of a substance from an area of high concentration to low concentration). If the blood has more oxygen than the tissues, oxygen will diffuse across the capillary walls and enter the tissues. Carbon dioxide and wastes are also removed from the tissues across the capillary walls, to the blood, where it travels to the lungs and is removed as you exhale.

The Digestive System The main function of this system is to absorb and transport nutrients throughout the body (all the way from the mouth to the anus). Absorption is the process by which food that has already been broken down passes through the walls of the intestine (mainly the small versus the large) into the bloodstream.

Digestive Organs Food Passage: Mouth → Tongue → Esophagus → Stomach → Small Intestines → Large Intestines → Rectum → Anus Mouth Lined with epithelial tissue and covered in glands that secrete mucus, saliva, and enzymes Tongue Made of epithelial tissues and glands, connective tissues, and muscle tissue

Digestive Organs (continued) Esophagus A tube of smooth muscles where food travels down from the mouth due to a rhythmic constriction and relaxation called peristalsis Lined with a protective layer of epithelial tissue Stomach Made of epithelial, connective, nervous, and muscle tissues The stomach churns food and mixes it with digestive juices (strong acids) and enzymes

Digestive Organs (continued) Intestines Both digestive nutrients and undigested waste products move into the small and large intestines, which are areas of chemical digestion and removal of wastes Solid wastes are then stored in the rectum and exit the body through the anus

Digestive System

Videos Respiratory System Respiratory Song to “Live While We’re Young” Circulatory System Circulatory Song to “Call Me Maybe” Heart Song to “Ho Hey” Digestive System Digestion Song to “Lightening”