Human Body Systems & Industrial Ergonomics

• The lecture discusses the systems of the human body and their importance in industrial ergonomics.
• It covers the history of human anatomy, key systems, and the skeletal system in detail

Systems of Human Body - Introduction and Background

• The study of the human body started in the fifth century BCE in Greece.
• Alcmaeon of Crotona was the first researcher to dissect a human body to find what was responsible for human intelligence.
• Alcmaeon proposed that the intellect resided in the head, contradicting the belief at the time that the heart was responsible for thought and awareness.
• He observed that head trauma seemed to lead to the loss of reasoning capability.
• In the third century BCE, Herophilus and Erasistratus expanded the field of anatomy through dissection.
• They were granted permission to perform vivisections on criminals.
• Leonardo da Vinci began making accurate anatomical drawings around 1489, with 750 drawings from the dissection of ~ 30 corpses.
• In 1628, Harvey Williams wrote about blood circulation instead of random drifting in "Exercitatio anatomica de motu cordis et sanguinis in animalibus".
• "Gray's Anatomy", or "Anatomy: Descriptive and Surgical" by Henry Gray and Henry Vandyke Carter, became the standard for anatomical literature in 1858.

Systems of the Body

• The human body is a complex organism made up of ten critical body systems.
• These systems include circulatory, respiratory, skeletal, muscular, nervous, immune, reproductive, urinary, digestive, and integumentary systems.
• A body system is a group of organs working to provide a specific function.
• Six systems that are central to ergonomics analysis are the circulatory, respiratory, skeletal, muscular, nervous, and integumentary (skin) systems.
• The systems perform singular and overlapping functions.

Circulatory System

• The circulatory system circulates blood and lymph through the body.
• The cardiovascular system is a subsystem of the circulatory system.
• It is a closed loop system where blood never leaves the network of blood vessels.
• The continuous flow of blood circulates repeatedly.
• The circulatory system transports nutrients, water, and oxygen to the cells, and carries waste products, such as carbon dioxide, away.
• The cardiovascular system is made up of the heart, arteries, arterioles, capillaries, and veins.

The Heart

• The heart, comprised of thick muscle tissue, is a main component of the cardiovascular system.
• Located in the center of the chest cavity slightly to the left of the sternum, it is about the size of a fist.
• With an average person’s lifetime, the heart beats approximately three billion times.
• It is divided into the top two chambers (atria) and bottom two chambers (ventricles).
• The right atrium receives blood first, and then contracts to force the blood into the right ventricle.
• Then blood is pumped out of the heart to the lungs.
• The atria contract at the same time as the ventricles.
• Blood comes into the heart through the superior and inferior vena cava.

Arteries

• The arterial system is the higher-pressure portion of the cardiovascular system.
• Arterial pressure varies with peak pressure during heart contraction (systolic pressure), and minimum or diastolic pressure between contractions.
• These pressures determine "blood pressure", which reflects the intensity of blood flow in the circulatory system.
• The arterial system consists of arteries and arterioles that carry blood away from the heart.
• With the exception of pulmonary and umbilical arteries, all arteries carry oxygenated blood.
• The arterial system is divided into:
• Systemic arteries that carry oxygenated blood to whole body
• Pulmonary arteries that carry deoxygenated blood to the lungs

Arterioles

• An arteriole is a small diameter blood vessel that extends and branches out from an artery to capillaries.
• The arterioles regulate the flow of blood in various parts of the body.
• They help to do body functions such as digestion and thermoregulation.
• Arterioles narrow to reduce blood flow to the skin to reduce heat loss when the body is cold.
• Arterioles expand to the digestive system during digestion for energy.

Capillaries

• Capillaries connect arterioles and venules and transport deoxygenated blood from the capillary beds to veins.
• The smallest blood vessels in the body, they measure 5-10 µm in diameter.
• They allow for the exchange of water, oxygen, carbon dioxide, nutrients and waste.
• They also enable the exchange of chemical substances between the blood and surrounding tissue.

Veins

• Arteries transport oxygenated blood to the muscles and organs, where nutrients and water are exchanged at capillaries.
• Veins transport deoxygenated blood from the organs and tissues back to the heart.

Blood Flow

• Blood flows through 4 chambers (upper right, lower right, upper left, and lower left), the lungs to remove waste (carbon dioxide) and oxygenate, and then the lower left ventricle.
• When the right ventricle contracts, blood is pumped into both lungs via the pulmonary artery (pulmonary circulation).
• The pulmonary artery carries deoxygenated blood.
• Blood returns from the lungs via pulmonary veins, which carry oxygenated blood.
• Blood is sent to the left ventricle when the left atrium contracts; the left ventricle is the strongest heart part.
• The left ventricle pumps blood into the aorta to circulate throughout the body.
• Oxygenated blood flows through arteries into arterioles and then into capillaries, where waste products are collected.
• Blood flows from capillaries into venules (small veins), then into the veins for the return trip to the heart.
• Veins return blood into the superior or inferior vena cava.
• The superior vena cava carries blood from the upper half of the body to the heart's right atrium.
• The liver and kidney remove waste products from the blood.
• The complex circulatory and cardiovascular systems provide oxygen delivery, waste removal, and fuel distribution.
• These systems support major systems to let bodily functions accomplish.

Respiratory System

• The respiratory system is for gaseous exchange, oxygenating blood and removing waste products like carbon dioxide.
• The respiratory system integrates with other systems, particularly the circulatory system, to accomplish its function.
• The respiratory system includes the mouth, nose, trachea, lungs, and diaphragm.
• The respiratory system interacts with the environment to receive oxygenated air.
• The mouth and nose allow oxygen to enter via the larynx and trachea.
• Oxygen flows to the bronchi, that branch off the trachea.
• Bronchi also divide into bronchial tubes, that flow into the lungs and disperse to the alveoli.
• Alveoli are tiny air sacs that number as high as 600 million in an adult.
• Oxygen diffuses through surrounding capillaries and then enters the arterial blood.
• Alveoli absorb carbon dioxide from waste-rich blood in the veins.
• Carbon dioxide leaves the lungs upon exhaling.

Skeletal System

• The skeletal system consists of bones and connective tissue to create the structure of the human body.
• It provides structural support, and protects internal organs from external force.
• It is divided into two components:
• Axial skeleton: the spine, ribs, sacrum, sternum, cranium, and about 80 related bones
• Appendicular skeleton: the bones of the arms, legs, pelvis, and shoulders, totaling 126 bones
• A human has ~350 bones at birth, but the average adult has 206 bones due to fusion.
• Ergonomics studies the bones of the extremities, skull, spine, and major joints.
• Bones are formed through ossification.
• Ossification is the actual activity of the bones.
• Calcification, confused with ossification, refers to the formation of calcium-based salts and crystals.
• Calcification occurs during ossification, but ossification cannot occur during the reverse.
• The human skeleton is primarily cartilage that is transformed into hard bone during infancy.
• Bones are classified as long, short, axial, or irregular.

Long Bones

• These are the bones of the extremities that consists of the shaft (diaphysis) and two ends (epiphyses).

Short Bones

• Short bones such as carpal bones in the hand or tarsal bones in the feet.

Axial Bones

• Axial bones are generally flat structures, such as those in the skull, pelvis, sternum, and ribs.

Irregular Bones

• Seen in the vertebrae.

Function of the Bones

• Bone supports the body, highly mineralized with 99% of the body's calcium.
• Bone's most important mechanical properties are stiffness and strength.
• The skeletal system begins to change in mineral content around 35 years of age.
• Decrease in bone mineral content and thickness results in bones that are susceptible to fracture and erosion around the joints.
• Primary functions are structure to the body, mechanical support for muscle attachment. stability for muscular forces, protecting organs.

Bone Failure

• Loading a bone to failure results in fractures and breakage from acute forces or low-level repetitive loading.
• Likelihood: the amount of load, level of repetition, and angle of loading.

Explore the systems of the human body and their significance in industrial ergonomics. Starting from 5th century BCE, anatomists like Alcmaeon and Leonardo da Vinci contributed to the understanding of human anatomy through dissection. Key body systems and the skeletal system are covered.