Human Body Systems 

Digestive System

General Info:

The digestive system is a complex network of organs and glands that processes food. In order for the body to get the nutrients and energy it needs, food must be broken down into smaller components that can be absorbed and used by the body. The digestive system includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus.

Pathway:

1. The digestive process starts when food is put into the mouth and chewed. The saliva in the mouth begins to break down the food, and the muscles in the mouth move the food to the back of the throat, where it is swallowed.
2. The food then travels down the esophagus, a muscular tube, to the stomach. In the stomach, the food is mixed with digestive juices that help to break it down further. The stomach produces acid and enzymes that break down proteins in the food.
3. The food then passes through the small intestine, where most of the nutrients from the food are absorbed into the bloodstream.
4. The large intestine absorbs water, vitamins, and minerals from the food and forms waste products, which are passed out of the body as feces. \n

The digestive system also includes several accessory organs that help with digestion. These organs include the liver, gallbladder, and pancreas.

• Liver: Responsible for filtering toxins from the blood, producing bile to aid digestion, and regulating fat metabolism.
• Gallbladder: Stores and concentrates the bile produced by the liver and releases it into the small intestine.
• Pancreas: Produces the enzymes needed to break down fats, proteins, and carbohydrates in the small intestine, and also produces the hormones insulin and glucagon, which are important for controlling blood sugar levels.

Respiratory System

The respiratory system is the system of organs and other structures in the body that allow us to take in oxygen and expel carbon dioxide.

The primary organs of the respiratory system are the lungs, which are made up of the bronchi, bronchioles, and alveoli.

• The bronchi are the large tubes that carry air from the trachea, or windpipe, to the lungs.
• The bronchioles are smaller tubes that carry air from the bronchi to the alveoli.
• The alveoli are tiny sacs in the lungs where oxygen and carbon dioxide are exchanged between the body and the atmosphere.

The respiratory system also includes the nose, the pharynx, the larynx, and the trachea.

• The nose is the organ that takes in air and warms, moistens, and filters it before it enters the lungs.
• The pharynx is the tube that connects the nose and mouth to the larynx and trachea.
• The larynx is the organ that produces sound and is also known as the voice box.
• The trachea is the tube that carries air from the larynx to the lungs.

The respiratory system also includes the diaphragm, a sheet of muscle that separates the chest cavity from the abdomen and helps to draw air into the lungs. The muscles of the chest wall and abdomen also play an important role in breathing. \n

The respiratory system includes pulmonary circulation, which is the circulation of blood through the lungs. In the lungs, oxygen is taken up from the air and carbon dioxide is expelled. The oxygen-rich blood then returns to the heart and is distributed to the rest of the body.

Nervous System

The nervous system is a complex network of specialized cells called neurons that transmit signals between different parts of the body. It is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory. \n \n The nervous system is divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).

• The CNS consists of the brain and spinal cord. It is responsible for processing information and controlling the body’s response to stimuli.
• The PNS includes all of the nerves that branch out from the CNS and connect it to the rest of the body.

Neurons are the cells that make up the nervous system. They are specialized to receive, process, and transmit information in the form of electrical signals. Neurons are highly adaptable and can change their structure and function in response to new information or experiences. \n \n The specialized cells of the nervous system are supported byglial cells, which provide structural and metabolic support.

• Glial cells also help to protect neurons from damage and can even repair damaged neurons.

The nervous system is also home to a variety of neurotransmitters, and chemicals that carry messages between neurons. Neurotransmitters play a key role in regulating mood, behavior, and cognition. \n \n The nervous system is closely connected to the endocrine system, which is responsible for secreting hormones into the bloodstream. Hormones help to regulate many of the body’s functions, including growth, metabolism, and reproduction.

Muscular System

The muscular system is composed of specialized cells called muscle fibers. These cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell.

• Muscles function to produce force and motion. They are responsible for maintaining and changing posture, locomotion, as well as the movement of internal organs, such as the heart.

Muscles are made up of three types of muscle fibers: skeletal, cardiac, and smooth.

• Skeletal muscles are attached to bones and are responsible for the movement of the skeleton.
• Cardiac muscle is found in the walls of the heart and is responsible for pumping blood throughout the body.
• Smooth muscle is found in the walls of organs such as the stomach and intestines and is responsible for involuntary movements such as digestion and urination.

Muscles are further divided into four distinct categories: slow twitch, fast twitch, intermediate, and mixed.

• Slow twitch fibers are used for endurance activities and have a low tension and long duration.
• Fast twitch fibers are used for explosive activities and have high tension and short duration.
• Intermediate fibers are a combination of the two and are used for activities that require a combination of speed and endurance.
• Mixed fibers are a combination of all three.

The muscular system works in conjunction with the skeletal system to produce movement. Muscles contract and relax in response to signals from the nervous system. When a muscle contracts, it pulls on the bones to which it is attached, causing the bones to move.

• Muscles also work in pairs, with one muscle contracting while the other relaxes, allowing for smooth, coordinated movements.

The muscular system is essential for movement and maintaining posture. It is also important for generating heat, which helps regulate body temperature.

• In addition, muscles play a role in protecting internal organs, producing hormones and other substances, and helping to circulate blood and lymph throughout the body. \n