Circulatory System

../_images/CirculatorySystem.jpg

Description

The Human Circulatory System is an artificial working model of the real human one. It consists of a four-chamber pump model that resembles a real heart in functionality and is connected to plastic tubes that resemble the blood vessels in the human body. The system is a fully automated mechanical system that is coded and controlled by Raspberry Pi.

Learning Objectives

The Human Circulatory System resembles in its function the one in real life. It helps students learn and apply the following:

  • Coding, electronics, robotics science, and Life science through a hands-on application that can be directly related to real life situations.
  • Anatomy of the human heart
  • Blood circulation throughout the body
  • Blood circulation through the lungs
  • Blood pressure, its cause and how it is different between arteries and veins
  • The role of valves in the heart
  • The change in heart beat and its effect on blood pressure
  • The implementation of the engineering design process
  • Application of theoretical concepts to real life situations

Materials Needed

  • Raspberry Pi with micro SD card and Raspbian
  • A 6V simple DC motors
  • A 6V rechargeable battery or 6V DC power supply
  • Integrated circuit (IC) L293D type
  • Jumper wires
  • Breadboard
  • Glue gun and glue sticks
  • Cutter blades or scissors
  • Sturdy wooden boards
  • Screws of various lengths
  • Screw drivers
  • Squeeze bottles
  • Rubber tubing
  • Plastic funnels
  • Small rubber balls
  • Bendable metal wires

Setup and Functionality

The Human Circulatory System runs on Raspberry Pi and uses a simple DC rotating motor that is attached off center to a circular piece of wood that rotates to increase and decrease the pressure on the plastic squeeze bottles. The speed of the rotation of the motor can be increased or decreased in order to relate it to changes in heartbeat.

Circuitry and Electronics:

The diagram below show all the wiring and connections of all the components used:

../_images/CirculatorySystem.png

Warning

Make sure to connect the wires properly on the L293D chip. In case the polarity is switched, the chip will get very hot and will be damaged. Avoid touching it and it might cause a skin burn.

Programming

import RPi.GPIO as GPIO
from time import sleep 
GPIO.setmode(GPIO.BOARD)
 
Motor1A = 19
Motor1B = 23
Motor1E = 21
 
GPIO.setup(Motor1A, GPIO.OUT)
GPIO.setup(Motor1B, GPIO.OUT)
GPIO.setup(Motor1E, GPIO.OUT)
 
try:
    
    while True:
        GPIO.output(Motor1A, GPIO.HIGH)
        GPIO.output(Motor1B, GPIO.LOW)
        GPIO.output(Motor1E, GPIO.HIGH)
        sleep(4)
        GPIO.output(Motor1A, GPIO.LOW)
        GPIO.output(Motor1B, GPIO.HIGH)
        GPIO.output(Motor1E, GPIO.HIGH)
        sleep(4)
except KeyboardInterrupt:
    GPIO.output(Motor1E, GPIO.LOW)
GPIO.cleanup()

Science Concepts and Skills

Cells are living entities that make up living things. The human body is made up of various types of cells based on their function. There are nerve cells, muscle cells, bone cells, skin cells, blood cells, sex cells, and others. Living cells have basic requirements in order to properly function and reproduce. This includes a supply of oxygen gas, nutrients, and water. At the same time, they need to get rid of carbon dioxide and wastes that are a product of the cells’ metabolic activities, such as cellular respiration.

The blood is responsible for the transport of all these materials in and out of the cell through blood vessels that reach every cell in the body. The organ that is responsible for pumping the blood through the blood vessels in the heart. The human heart is made up of two separate parts, the left and the right. Each part has two chambers has two chambers, the atrium and the ventricle, where blood moves from the atrium to the ventricle through a valve that ensures blood flow in one direction.

The figure below shows the anatomy of the human heart. It is divided into four main chambers, the left atrium and the left ventricle, the right atrium and the right ventricle. Each atrium is connected with to the ventricle through a valve.

../_images/CirculatorySystem-CrossSection.jpg

The blood circulation through the heart goes through two routes to ensure that oxygen is replenished and carbon dioxide is released out of the body through the lungs.

Pulmonary circulation transports the blood that had been already circulating through the body that has given its oxygen to the cells and collected carbon dioxide. It is referred to as deoxygenated (blood rich in carbon dioxide). It circulates from the right side of the heart to the lungs, where the blood picks up oxygen and returns to the left side of the heart. The pumping chambers in this case are the right atrium and right ventricle. Systemic circulation carries oxygenated blood (blood rich in oxygen) from the left side of the heart to all the body cells and tissues. Through systemic circulation, blood removes wastes and carbon dioxide from body tissues and returns deoxygenated blood to the right side of the heart. The left atrium and left ventricle of the heart are the pumping chambers for the systemic circulation.

The valves between the atria and the ventricles ensure that blood flows only in one direction.

The rate of the heartbeat and the constriction and dilation of the blood vessels, as well as other factors, affect the blood pressure of the body that will cause it to either increase or decrease. More information at the link:

Tutorial Video.

The Human Circulatory System project resembles in its structure and function that of a real one.

The 6V DC motor circulates back and forth in half rotations. Each half rotation either causes the right and the left ventricles to contract and the atria to relax (squeeze bottles), or vice versa. This causes the fluid in the tubes (resembling blood) to go through the systemic and the pulmonary circulations. The rate of the pumping can be altered by changing the speed of the motor, which resembles the change in heartbeat. This shows how the change in heartbeat affects the rate of flow of blood in the vessels and the change in pressure.

The fluid in the system moves in one direction as the ventricles or the atria contract due to the presence of valves between each atrium and ventricle and between the ventricles and the arteries that leave the heart to the body or lungs. These valves are made of simple rubber balls that are placed in a plastic funnel and closes the opening. It opens to allow flow when pressure of the fluid increases in the atrium due to its contraction and decreases in the ventricle due to its relaxation. It closes when pressure increases in the ventricle due to its contraction and decreases in the atrium due to its relaxation to ensure that the fluid flows out to the body or lungs when ventricles contract.

Flex your brain! Can you build a similar device that will aid patients in respiration?