Introduction to the Human Body
Introduction to the Human Body
Orientation
The human body is often thought of as a single entity, which is serviceable for ecological understanding, but for finer functions of anatomy and physiology, it's a composition of many things.
The human body is composed of individual units (cells) that cooperate, work together, and sometimes compete.
The human body contains approximately 30 to 40 trillion integrated cells.
Cells are the living components of the human body, with metabolism, chemical processes, and divisions.
Bone's rigidity and strength come from inorganic components like minerals and proteins.
Living and non-living components combine to form the body's composition.
Human cells vary in size.
80% of cells by number are red blood cells (erythrocytes), but they only account for 4% of total body mass due to their small size.
Microbiome and Virome
The human body includes the microbiome, trillions of microorganisms that live within and on us.
Microorganisms outnumber human cells by approximately 10 to 1, but only represent 1-3% of total body mass.
For a 200-pound individual, 2-6 pounds are microorganisms like bacteria.
The human body also has a virome, the collection of all viruses within the human body, which participates in overall structure, function, and health.
Understanding conditions and functions often requires referring back to the cellular scale.
Microbiological Colonies on the Body
The slide shows microbiological colonies on the surface of the human body.
Each unique color represents a unique microbiological colony on that body part.
Elemental Composition of the Human Body
The human body is made of elements from the periodic table.
The human body consists of elements like oxygen, carbon, hydrogen, and nitrogen in varying percentages.
Oxygen, carbon, and hydrogen are abundant but become valuable when organized as the human body.
The organization of elements brings a value exceeding their material basis.
The relationship exists between substrate (materiality) and the pattern/density of information expressed within the physical construct.
Hierarchy of Organization
The human body can be studied at different scales.
Atomic level: atoms in the body
Molecules: atoms interact to form molecules.
Simple molecules: water ( - two hydrogen atoms and one oxygen atom).
Complex molecules: macromolecules (proteins, carbohydrates)
Organelles: molecules interact to form elaborate structures in cells
Cells: combination of molecules.
Tissues: cells with similar functions group together.
Examples: fat tissue, muscle tissue, nervous tissue.
Organs: tissues organize into organs.
Example: heart (muscle, adipose, connective, epithelial tissues).
Organ systems: organs interact together.
Example: cardiovascular system (heart and blood vessels).
Organism: organ systems function together to create the human organism.
Evolution: Biological and Cultural/Technological
Biological evolution: organisms change over time; organisms can speciate given enough time and change.
Cultural/technological evolution: evolution from simple tool use to computers.
Both forms of evolution refer to change and interact with each other.
Cultural state can impact biological state, e.g., computer use vs. physical effort for calories.
Evolutionary theory helps understand human body structure and function.
Definition of Life
Living organisms are self-organizing and maintaining (autopoiesis).
If you injure a finger, processes will enact healing.
If you tear a piece of paper, spontaneous recovery does not occur.
Cell theory: life is made of independent structures referred to as cells.
To be alive, you must have a cell.
Viruses are not cells but possess living characteristics.
Whether something is living is determined by the degree to which it evidences certain characteristics.
Characteristics of Life
Responsiveness: responding to stimuli (e.g., raising hand when called).
Conductivity: flow of information through a system
Conversion of vibrations into electrochemical activity and movement to the brain
Growth: addition or replacement of biological materials.
Respiration: exchange of oxygen and carbon dioxide in a biological system (energy processing).
Digestion & Absorption: breaking down food into smaller, absorbable pieces (mechanically or chemically), and incorporating it into the body.
Secretion & Excretion: releasing materials (sweat, tears, hormones), and removing waste products (urine, feces).
Circulation & Reproduction:
Cardiovascular system: circulates blood.
Lymphatic system: circulates lymphatic fluid (immune responses).
Reproduction: species propagation sexually and/or asexually.
Functional definition is useful for defining what is and isn't living.
Scientific Method
The scientific approach attempts to falsify a testable claim.
Failure to falsify supports the opposite claim.
The opposite claim isn't necessarily entirely true.
Open-endedness allows for the development and evolution of understanding.
Anatomy
Anatomy is the study of the structure of an organism and its discrete parts.
Anatomy uses diagrams or models with identified/named parts.
Types of anatomy:
Gross anatomy: study with the naked eye.
Cytology: study of cells (microscope required).
Histology: study of tissues (microscope required).
Physiology
Physiology is the study of how anatomical parts of the body exist in relationship to each other functionally.
Dynamic and kinetic elements.
Anatomy is instrumental to understanding physiology.
Homeostasis
Homeostasis is the maintenance of relatively constant internal conditions despite external and internal environment changes.
Example: staying at stable body temp in either cold or hot environments
Blood Sugar Control (Glucose)
In a healthy individual, glucose fluctuates between 80-100mg/mL
Normal range of glucose in human blood. The set point (average value) for glucose is 90 mg/mL, but fluctuates throughout the day.
Low Glucose levels:
Expenditure of energy without glucose intake - curve goes low towards 80.
Behavioral responses: feeling tired, irritable, hangry.
Drive to eat to replenish glucose.
Biological responses: release of stored glucose from liver and skeletal muscle (glycogen).
Hormone glucagon is released to mobilize glucose into the blood and increase levels.
High Glucose Levels:
Consumption of high burning sugar - curve goes high towards 100.
Behavioral responses: feeling jittery and energetic and wanting to move around to burn energy.
Biological responses: mechanism for depositing extra glucose from the blood into storage in the form of glycogen into the skeletal muscle and liver.
Insulin is released.
The curve is a dynamic up-and-down dependent on what is being tweaked and adjusted at that particular part of the day for this given individual, it isn't a straight line.
Homeostasis is the regulation or the attempt to regulate a certain variable for some amount of time against fluctuating environmental conditions.
Homeostasis Variables
Many variables in the body need regulation regarding homeostasis.
Blood panel (blood work) shows variables, results, and limits.
Conscious attention cannot regulate the variables as it's not dependent on it.
Feedback Control Loops
Homeostasis is maintained through feedback control loops with interacting components.
Components of Feedback Control Loop: sensor mechanism (detects change), and a control center (acts on information) and an effector (causes work to change the variable).
Body Temperature Regulation Example
Temperature Drops
Temperature drops sharply.
Temperature receptors in the skin detect temperature change.
Receptors forward information to the brain (hypothalamus).
The hypothalamus (integrator) will respond by sending a message over to the skeletal muscles to contract rapidly.
Skeletal muscles are stimulated to rapidly contract (thermogenic shivering).
Shivering produces heat to compensate for heat loss.
Variable: dropping temperature.
Sensor: skin receptors.
Integrator: brain (hypothalamus).
Effector: muscle tissue.
When temperature drops, the response is an attempt to oppose.
Temperature Rises
Environment temperature rises.
Skin receptors detect temperature increase.
Information is sent to the brain (integrator) that temp. is too high.
The effector (sweat glands) release water onto body surface.
Water takes up heat and changes from liquid to gas, cooling the body down.
This can be described as a negative feedback system.
Negative Feedback Systems
Oppose a change by creating a response opposite in direction to the initial disturbance.
Tend to be inhibitory.
Temperature and glucose control are examples of negative feedback systems.
Positive Feedback Systems
Amplify or reinforce the change occurring in the body.
Have a stimulatory effect.
Labor:
Baby growing in the uterus and growing to a certain size will trigger messages from the uterine wall to the brain that the stretch is reaching a critical point.
The brain receives information from stretch receptors in the uterus.
In response to receiving that communication from the stretch receptors in the uterus, the brain will actually release a molecule referred to as oxytocin (OT).
Oxytocin (OT) causes uterine wall to contract.
Increased contraction increases the stretch that initiated the mechanism.
The uterus will once again communicate with the brain and inform it of the increasing stretch and the brain will once again release oxytocin.
The loop increases pressure in the uterus and facilitates labor.
Feedback ultimately reduces the stretch to lower to initial levels after the baby leaves the uterus and therefore is in the service of negative feedback.
Pathophysiology
Disturbances to homeostasis can be thought of as illness if they are temporary.
Permanent failure of homeostasis results in death.
Pathophysiology is the study of the body when physiological processes are those associated with disease.
Concerns are with looking at the body and its diseased condition.
Causes of Disease: genetics, pathogens (viruses, bacteria), cancer, malnutrition, inflammation, degeneration, age, lifestyle, stress.
Pathophysiology Examples
HIV Virus:
The HIV virus is destroying a white blood cell.
Hijacks white blood cell and programs it to produce more virus.
Amplifies virus and destroys defense mechanisms.
Localized Tumor:
Large lump/growth at the back of the neck.
Tumor was membrane bound and localized, after treatment, it's excised (removed).
Porphyria:
Collection of genetic disorders affecting blood.
Allergic reaction to the sun (damaged, blistered skin, irritated).
Trouble sustaining hair follicles (hair loss due to lack of oxygen).
Gum tissue is destroyed/disfigured (teeth look larger).
Experiencing a thirst for blood (Anemic, locking in iron).
Behaviorally speaking, would tend to be people who would avoid the light. They would tend to look a little bit strange and potentially have odd predilections for diet.
Porphyria is a collection of genetic disorders where blood characteristics are affected, the description is similar to the original conception of Nos Veratu (vampires).