Intro to Anatomy and Physiology - BIOL 310
THE BASICS OF BODY STRUCTURE AND FUNCTION
Learning Goals
• Describe, in order, from simplest to most complex, the major levels of organization in the human body
• Explain the general principle that form and function are related in anatomy and physiology, and be able to give examples at all levels of organization (molecular > organ system)
Shape and Job: The Perfect Duo
The main rule in biology is that form follows function. This means a body part is built specifically to do a certain task.
Example: The Heart
The Job: The heart pumps blood to move nutrients and oxygen everywhere in the body.
The Build: It is split into four rooms: the Right Atrium (RA), Right Ventricle (RV), Left Atrium (LA), and Left Ventricle (LV).
The Reason: Having separate rooms stops oxygen-rich blood from mixing with oxygen-poor blood.
The Path of Blood
Blood without oxygen arrives from the body into the Right Atrium.
It moves to the Right Ventricle and is sent to the lungs to pick up oxygen.
The new oxygen-rich blood comes back to the Left Atrium.
Finally, it goes to the Left Ventricle, which pumps it out through a big tube called the Aorta to the rest of the body.
Learning from History
Long ago, Leonardo Da Vinci drew detailed pictures of heart valves, showing how their shape helped control blood flow.
Different Types of Cells
Human cells can look very different when zoomed in times:
Digestive Cells: These are very thin and delicate so they can easily soak up vitamins and water from food.
Sex Cells: Women have a few large eggs (oocytes) produced monthly; men produce millions of tiny sperm constantly.
Nerve Cells (Neurons): These act like tiny computer chips, sending signals for memories and movement. They come in many shapes based on their specific job.
Fat Cells: These look like round balloons that swell up when the body stores extra energy from food.
How Cells Work and Talk
Heart Muscle Cells: They have special connectors called intercalated discs so they can all squeeze together at the exact same time.
Muscle Movement: Muscles move because of a cycle involving proteins like myosin and specific chemical reactions.
Cell Signals: The cell's "skin" (membrane) has locks that wait for chemical keys.
For example, a chemical called acetylcholine () hits a muscle cell, opening a gate for sodium ions () to enter, which tells the muscle to contract.
Survival and Changing Over Time
Anatomy and physiology work together to keep your body stable and healthy (homeostasis).
Homeostasis: the state of balance within the body systems.
It is essential for maintaining stable internal conditions despite external changes.
Importance of Homeostasis
Maintaining balance is crucial for overall health and functionality.
Imbalances can lead to various health issues.
Behavior counts: How an animal acts is just as important as how it is built.
Example: Hummingbirds: They have long beaks for flowers, fast digestion for sugar, and a super-fast metabolism to keep their energy up.
Human History and Evolution
Human Changes: Since humans split from a shared relative with apes about million years ago, two big things happened:
Humans started walking on two legs (bipedalism).
Human brains got much bigger.
Common Myths: Humans did not come from chimpanzees. Instead, both humans and apes share a common ancestor from long ago and then evolved into different groups.
Why Walking on Two Legs Matters
Walking upright was the first major change. To do this, the human body adapted with:
A short, wide pelvis to hold muscles in place.
Long leg bones (femurs) that tilt inward toward the knees.
Feet with arches to support weight.
The Cost of These Changes: Because we walk upright, humans often suffer from back pain (like herniated discs), knee problems, and difficult childbirth because the pelvis is narrow and baby heads are large. Walking Gait Terminology Definitions
• Stance phase: When a foot is on the ground (for example, L foot stance phase)
• Swing phase: When a foot is not on the ground, but swinging forward toward its next
heelstrike (for example, L foot swing phase)
• Double support: When both feet are on the ground
• Single support: When only one foot is on the ground
• Running is differentiated from walking by having an aerial phase, when neither foot is on
the ground.
• Heel strike: When the heel of the leading foot first hits the ground at the beginning of
stance phase.
• Midstance: When the body is balanced over the vertical stance leg, and the other leg is
in the middle of swing phase.
• Toe off: When the big toe of the trailing foot comes off the ground at the end of stance
phase. This is the beginning of swing phase.
• Stride: From heelstrike of one foot to the next heelstrike of the same foot.
• Step: From heelstrike of one foot to the next heelstrike of the other foot.
Summary
How we are built and how we function today is the result of millions of years of evolution. This history explains why our bodies work the way they do and why we face certain health issues.