Name: lungs, airways, and gas exchange
Uploaded: 2025-10-23T11:49:11.000Z
Duration: 1 min 16 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Human Anatomy and Physiology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.HA.1.9

The Respiratory System

The respiratory system consists of a series of passageways and ducts that bring air from the outside of the body to the lungs inside.

Air first enters through the nostrils and into the nasal cavity where particulate matter, potentially harmful to breathe like bacteria and dirt, is filtered out by hairs and mucus and cleaner air is warmed and humidified.

Air can also flow through the mouth, reaching the pharynx and larynx before being funneled into the main airway, the trachea.

As the trachea leads into the thoracic cavity, the ends bifurcate into two bronchi, corresponding to the left and right lungs, which are surrounded by pleural membranes and bound inferiorly by the diaphragm.

Within each lung a bronchus splits into increasingly smaller branches called bronchioles. At the smallest tips are alveolar ducts subdivided into tiny sacs of alveoli, thin layers of parenchymal cells.

Such organization provides a large surface area for gas exchange to occur with the circulatory system.

the respiratory system

The respiratory system is comprised of the organs that enable breathing. Air enters the nostrils and mouth, followed by the pharynx (throat) and larynx (voice box), which lead to the trachea (windpipe). In the thoracic cavity, the trachea splits into two bronchi that allow air to enter the lungs. The bronchi split into progressively smaller bronchioles and terminate in small groups of tiny sacs in the lungs called alveoli, where gas exchange occurs.

<h4>Removal of Debris</h4>

Air is cleansed in the nasal cavity, but anything that passes those defenses or enters through the mouth can be caught in the lungs. The lungs produce mucus that traps foreign particles, and the bronchi and bronchioles are lined with cilia that beat mucus and debris upward toward the throat for disposal (i.e., swallowing). Smoking damages the cilia, making removal of the excess mucus produced by smoking more difficult. This is one of the reasons smokers are more susceptible to respiratory infections.

<h4>Trachea</h4>

The trachea is a 10-12 cm long tube located in front of the esophagus that allows air to enter and exit the lungs. Its C-shaped hyaline cartilage keeps the trachea open. When the smooth muscle of the trachea contracts, the diameter of the trachea decreases and exhaled air is pushed out with great force (e.g., coughing). In cases of damage to the throat or mouth that blocks breathing, a tracheostomy, a surgically-created hole in the trachea, can allow air into and out of the lungs.

<h4>Alveoli</h4>

A single alveolar duct at the end of a bronchiole divides into approximately 100 alveolar sacs, which each resembling a bunch of grapes on a stem. Each alveolar sac has 20-30 alveoli, which look like little bubbles, or grapes. Alveoli are the sites of gas exchange and have direct contact with capillaries. This structure is crucial to the function of the lungs&#8212;providing the body with oxygen and removing carbon dioxide&#8212;because it maximizes the surface area of the lungs. The lungs contain 75 m2 of alveoli surface area, the size of a small apartment!

The respiratory system is comprised of the organs that enable breathing. Air enters the nostrils and mouth, followed by the pharynx (throat) and larynx ...

Education

JoVE Core

Biology

Human Biology

Circulatory and Pulmonary Systems

KEY TERMS AND CONCEPTS

lungs, airways, and gas exchange

The respiratory system moves air through the airways and into the lungs. Air enters through the nostrils and mouth, then passes the pharynx, or throat, and the larynx, or voice box. From there, it travels into the trachea, also called the windpipe.

Inside the thoracic cavity, the trachea splits into two bronchi. These tubes carry air into the lungs. The bronchi divide into smaller bronchioles, which end in tiny air sacs called alveoli. Gas exchange happens in the alveoli.

The respiratory tract also helps remove debris. The nasal cavity cleans the air first, but particles that get past it or enter through the mouth can still be trapped in the lungs. The lungs make mucus that catches foreign material. The bronchi and bronchioles have cilia, which are tiny hairs that move mucus and debris upward toward the throat so it can be swallowed. Smoking damages the cilia and makes it harder to clear extra mucus. That is one reason smokers are more likely to get respiratory infections.

The trachea is a 10-12 cm tube in front of the esophagus that lets air move in and out of the lungs. C-shaped hyaline cartilage keeps the trachea open. When the smooth muscle of the trachea contracts, the airway becomes narrower and exhaled air is forced out with great power, such as during coughing. If damage to the mouth or throat blocks breathing, a tracheostomy can create a surgical opening in the trachea so air can still reach the lungs.

Alveoli are the sites of gas exchange. A single alveolar duct at the end of a bronchiole divides into about 100 alveolar sacs, and each sac contains about 20-30 alveoli. They look like tiny bubbles or grapes, and each alveolar sac resembles a bunch of grapes on a stem. Alveoli touch capillaries directly, which helps the body take in oxygen and remove carbon dioxide. Their structure gives the lungs a very large surface area, about 75 m2, which is roughly the size of a small apartment.

Lungs, Airways, and Gas Exchange

The respiratory system moves air through the airways and into the lungs. Air enters through the nostrils and mouth, then passes the pharynx, or throat, and the larynx, or voice box. From there, it travels into the trachea, also called the windpipe. Inside the thoracic cavity, the trachea splits into two bronchi. These tubes carry air into the lungs. The bronchi divide into smaller bronchioles, which end in tiny air sacs called alveoli. Gas exchange happens in the alveoli. The respiratory...

breathing

How Air Moves In and Out of Lungs

Breathing depends on pressure changes in the chest, the lungs, and the muscles that move them. The diaphragm, which sits below the lungs, and the intercostal muscles, which are between the ribs, work together to change the size of the thoracic cavity. When the diaphragm contracts, it moves downward. When the intercostal muscles contract, the ribs move upward and the rib cage expands. Both actions increase thoracic volume and give the lungs more room to expand. Each lung is surrounded by two...

lung capacity

Lung Volume and Capacity Measures

Lung volume and lung capacity describe how air moves through the lungs and how much air stays inside them. Lung volume measures the amount of air taken in, released, or left over after a lung action, such as one breath. Lung capacity is a sum of two or more lung volume measures. There are four lung volumes. Tidal volume is the amount of air inhaled and exhaled in a normal breath. Inspiratory reserve volume is the extra air that can be inhaled after a regular breath in. Expiratory reserve...

gas exchange and transport

Alveoli and Capillaries in Gas Exchange

Gas exchange depends on the movement of oxygen and carbon dioxide between the lungs and the blood. During respiration, gases move along pressure gradients, which means they travel from higher partial pressure to lower partial pressure. In mammals, this exchange takes place in the alveoli of the lungs, where air and blood come very close together. When the lungs expand, pressure inside the lungs drops below atmospheric pressure. That drop draws oxygen-rich air into the lungs. The air in the...

anatomy of the circulatory system

Circulatory Pathways of the Heart and Blood

The human circulatory system moves blood through the heart, blood vessels, and the body. The heart works as a central pump. Blood vessels carry blood away from the heart, around the body, and back again. Humans have a double circulatory system. Blood travels through the heart twice as it moves through the pulmonary circuit and the systemic circuit. The pulmonary circuit sends blood between the heart and lungs. In the pulmonary capillaries, oxygen enters the blood and carbon dioxide leaves it. <br...

anatomy of the heart

Heart Chambers, Valves, and Blood Flow

The human heart has three tissue layers and is surrounded by the pericardium, a membrane that protects and confines it. The outermost layer, closest to the pericardium, is the epicardium. A pericardial cavity separates the pericardium from the epicardium. Beneath the epicardium is the myocardium, which is the middle layer. The innermost layer is the endocardium. The heart also has four chambers: the right atrium, right ventricle, left atrium, and left ventricle. These chambers contain two...

the cardiac cycle

How the Heart’s Beat Is Controlled

The heart’s beat is controlled by a repeating electrical pattern called the cardiac cycle. It combines contraction, or systole, with relaxation, or diastole. This rhythm keeps blood moving through the heart in a steady sequence. The cycle begins when electrical signals leave the sinoatrial, or SA, node in the wall of the right atrium. The signal spreads to the atrioventricular, or AV, node between the right atrium and right ventricle. This causes both atria to contract at the same time. When...

blood flow

Blood Flow Through Vessels

Blood flow moves from the heart into the aorta, the largest artery in the body, and then into smaller arteries, arterioles, and capillaries. As the vessels get smaller, the speed of blood flow decreases. When blood returns to the heart through venules and veins, its velocity increases again. This change in speed is linked to total cross-sectional area, which is the combined area of all the vessels in a group. Blood does not move from one vessel into just one smaller vessel. It spreads into...

key terms and concepts

Learn how air travels through the airways, how cilia and mucus remove debris, and how alveoli exchange oxygen and carbon dioxide in the lungs.

Lungs, Airways, and Gas Exchange | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

new-york-state-science-learning-standards

New York State Science Learning Standards

High School

Life Science

Structure and Function

HS-LS1-2.

myJoVE Corporation

structural-organization-of-the-human-body-an-overview

Structural Organization of the Human Body: An Overview

It is convenient to consider the body&#39;s structures in terms of fundamental levels of organization that increase in complexity: subatomic particles, ...

Tissues

Tissues are a group of cells that share a common embryonic origin. Microscopic observation reveals that the cells in a tissue share morphological features ...

Cells with similar structure and function are grouped into tissues. A group of tissues with a specialized function is called an organ. There are four main ...

Mitochondria

The Endoplasmic Reticulum

Introduction to Cytoskeleton

What are Membranes?

1. Obtain, evaluate, and communicate information to explain how differences in cellular structure (mitochondria, cytoskeletal structure, endoplasmic reticulum, cell membrane) lead to differences in the function and organization of the four tissue types (epithelial, connective, muscular, and nervous).

9-12.HA.1.1

Introduction to the Integumentary System

The integumentary system is the organ system that comprises the skin and its associated structures. It is the largest system in the human body and plays a ...

Cells of the Epidermis

The epidermis is made of four or five layers of epithelial cells, depending on its location in the body. From deep to superficial, these layers are the ...

Papillary Dermis

Dermis
The dermis might be considered the &#34;core&#34; of the integumentary system, as distinct from the epidermis and hypodermis. It contains blood and ...

Layers of the Epidermis

The epidermis, the outermost layer of the skin, is composed of several distinct layers. From deep to superficial, the layers of the epidermis are as ...

accessory-structures-of-the-skin-sweat-glands

Accessory Structures of the Skin: Sweat Glands

Sweat glands or sudoriferous glands are one of the important accessory structures of the skin. They are small, coiled tubular structures located in the ...

accessory-structures-of-the-skin-hair-and-hair-follicles

Accessory Structures of the Skin: Hair and Hair Follicles

Hair and hair follicles are integral components of the integumentary system. Hair is a filamentous structure composed mainly of a protein called keratin. ...

Accessory Structures of the Skin: Nails

Nails are one of the important accessory structures of the skin. They are hard, protective structures that cover the dorsal surface of the distal ...

2. Obtain, evaluate, and communicate information to describe how the structures of the integumentary system and its accessory organs contribute to its function. Examples: how the layers of the skin contribute to homeostasis, the role of glands in thermoregulation and in hydration of skin and mucous membranes, the protective functions of hair and nails

9-12.HA.1.2

Thermoregulation

The body regulates core temperature through negative feedback mechanisms.
When the core temperature drops, thermoreceptors send signals to the ...

Defense Mechanism Against Infection

Natural flora, body system defenses, and inflammation are natural barriers of the body against infectious agents regardless of previous exposure. Normal ...

Surface Membrane Barriers

Surface barriers such as the skin and mucous membranes are the body&#39;s initial defense against pathogens, offering physical and chemical protection.
...

a. Construct an explanation of the relationships between the integumentary system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain how changes in vessel diameter and evaporation of water over the skin contribute to thermoregulation (cardiovascular). Explain how sweat is used to excrete nitrogenous waste from the blood (cardiovascular). Explain how the skin and mucous membranes create a barrier against infection (immune system).

9-12.HA.1.2.a

Introduction to the Skeletal System

The skeletal system is the central framework of the body, consisting of different connective tissues: bones, cartilage, tendons, and ligaments.
Components ...

Classification of Bones

The bones of the human skeletal system are of varied shapes, sizes, and functions. They can be classified based on their shape and function into four ...

Overview of the Axial Skeleton

The skeleton is subdivided into two major divisions&#8212;the axial skeleton and the appendicular skeleton. The axial skeleton forms the vertical, central ...

Introduction to Joints

The adult human body usually has 206 bones, and except for the hyoid bone in the neck, each bone is connected to at least one other bone. Joints are the ...

Joints

Joints, also called articulations or articular surfaces, are points at which ligaments or other tissues connect adjacent bones. Joints permit movement and ...

3. Develop and use a model to illustrate how the structures of the skeletal system contribute to its function. Examples: Create a diagram or 3D model to illustrate bone shape, joint types, and bones in the appendicular and axial skeletons. Use models to illustrate the role of the skeletal system in movements around joints, support of a body structure, and protection of soft tissues.

9-12.HA.1.3

bone-formation-by-endochondral-ossification

Bone Formation by Endochondral Ossification

Bone formation, or ossification, begins around the sixth to seventh week of embryonic development. Most bones develop from a cartilaginous template ...

bone-formation-by-intramembranous-ossification

Bone Formation by Intramembranous Ossification

Intramembranous ossification is one of the two processes involved in the development of bones within an embryo. The flat bones of the face, most of the ...

Bone Remodeling and Repair

a. Obtain, evaluate, and communicate information describing the growth and development of the skeletal system.

9-12.HA.1.3.a

The Functions of the Skeletal System

The most apparent functions of the skeletal system are support, protection, and movement. However, bone tissue also performs several other critical ...

Skeleton and Calcium Homeostasis

Calcium is not only the most abundant mineral in bone but also the most abundant mineral in the human body. Calcium ions are needed for bone ...

The Bone Matrix

Bone contains a relatively small number of cells entrenched in a matrix of collagen fibers that provide an adherent surface for inorganic salt ...

Overview of Hematopoiesis

Hematopoiesis, or hemopoiesis, is the production of the formed elements in blood from common progenitors, called hematopoietic stem cells, or HSCs.
During ...

b. Construct an explanation of the relationships between the skeletal system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain the role of spongy bone in hematopoiesis (cardiovascular system) and leukopoiesis (immune system). Explain how the storage of minerals in bone contributes to homeostasis.

9-12.HA.1.3.b

The Muscular System

The muscular system includes the skeletal, smooth, and cardiac muscles that coordinate with each other to carry out functions like movement, digestion, ...

Naming Skeletal Muscles

Skeletal muscle names are based on various factors, such as location, physical traits, and functions.
Often, muscle names indicate their location. For ...

Muscle Coordination and Action

The skeletal muscles can coordinate, oppose, or assist each other to facilitate voluntary body movements.
Depending on their function, a muscle or group ...

Fascicle Arrangement in Skeletal Muscles

Fascicles are bundles of muscle fibers in a skeletal muscle. Muscle fascicle arrangement is directly associated with the power and range of motion of ...

4. Develop and build a three-dimensional model to illustrate the structures of the muscular system, including muscle locations, origins, and insertions, and explain their roles in movement and support. Example: Design and build a model of a lever to illustrate the relationship between bones and muscles and explain their roles in body movement and support.

9-12.HA.1.4

Microscopic Anatomy of Skeletal Muscles

Each skeletal muscle is composed of multiple bundles of elongated multinucleated muscle cells or muscle fibers.
These cells are enclosed by a plasma ...

The Sarcomere

A sarcomere is mainly made up of two types of filaments&#8212; thin filaments containing actin, troponin, and tropomyosin and thick filaments containing ...

excitation-contraction-coupling-in-skeletal-muscles

Excitation-Contraction Coupling in Skeletal Muscles

Excitation-contraction coupling is a series of events that occur between generating an action potential and initiating a muscle contraction. It occurs at ...

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions ...

a. Model the cellular physiology of skeletal muscle, including how the cell functions in muscle contraction and relaxation. Example: Use straws and paper to create a model of a sarcomere to illustrate how the fibers move during contraction and relaxation.

9-12.HA.1.4.a

Muscle Recovery and Fatigue

Any intense physical activity escalates the ATP demand in the muscles.
As contractions become vigorous, the compressed blood vessels impair the ...

Muscle Stimulation Frequency

Depending on the demand, motor neurons control the strength of a muscle&#39;s contraction by altering the frequency of action potentials delivered to the ...

b. Obtain, evaluate, and communicate information to explain muscle fatigue and tone in terms of muscle cell physiology.

9-12.HA.1.4.b

Organization of the Nervous System

The nervous system is the primary control and communication center of the body.
The nervous system can be divided into two major categories&#8212;the ...

functional-divisions-of-the-nervous-system

Functional Divisions of the Nervous System

The nervous system senses, integrates, and responds to various stimuli. Based on bodily control, the central nervous system cannot be divided ...

Anatomy of the Brain: Major Regions

The human brain is a complex organ consisting of four main parts &#8212; the cerebrum, the cerebellum, the diencephalon, and the brainstem.
The cerebrum ...

peripheral-nervous-system-ganglia-and-nerves

Peripheral Nervous System: Ganglia and Nerves

The peripheral nervous system consists of nerves, ganglia, and sensory receptors.
Each nerve has an outermost connective tissue layer called the ...

5. Obtain, evaluate, and communicate information explaining the relationship between the structures and functions of the central nervous system and the peripheral nervous system.

9-12.HA.1.5

Action Potential

Neurons communicate by firing action potentials&#8212;the electrochemical signal that is propagated along the axon. The signal results in the release of ...

Propagation of Action Potentials

The Propagation of an action potential is the process by which a nerve impulse is transmitted along the axon. It is a self-propagating process; once ...

Action Potential: Phases of Stimulation

The action potential is a complex electrical event that occurs in excitable cells, such as neurons and muscle cells. It consists of several distinct ...

Voltage-gated Ion Channels

a. Use a model to illustrate the role of action potentials in neural transmission. Clarification: Discussions of sodium-potassium pumps and ion channels are not required.

9-12.HA.1.5.a

Somatic Spinal Reflexes

Somatic spinal reflexes are rapid, involuntary muscular responses to external stimuli that involve the somatic musculature and the spinal cord.
One of the ...

Reflex Activity

A reflex is a quick and automatic response to a stimulus, like pulling your hand away from heat or lifting your foot off a sharp object.&#160;&#160;
A ...

Introduction to Special Senses

Humans have five special senses&#8212;vision, smell, taste, hearing, and equilibrium. All these senses have anatomically distinct receptors to detect ...

b. Construct an explanation of the role of reflex arcs, the central nervous system, and special senses in the response to stimuli to maintain homeostasis and guide behavior. Example: smelling a strong odor initiating a sneeze response using a reflex arc; pupil diameter changing in relation to the amount of light entering the eye Clarification: Discussion of the anatomy and physiology of the sensory organs is not required.

9-12.HA.1.5.b

Neurotransmitters

Neurotransmitters play a crucial role in the communication between neurons in the autonomic nervous system. Neurons in the autonomic nervous system can be ...

Chemical Synapses

Chemical synapses are specialized sites between two neurons or between a neuron and a non-neuronal cell like a muscle, glandular or sensory cell.
Because ...

The Synapse

Neurons communicate with one another by passing on their electrical signals to other neurons. A synapse is the location where two neurons meet to exchange ...

c. Construct an explanation of the role of neurotransmitters in the functions and behavior of the nervous system. Clarification: Discussion of classes of neurotransmitters is not required.

9-12.HA.1.5.c

Functional Brain Systems: Limbic System

The limbic system is a functional brain region consisting of specific parts of the diencephalon and cerebrum.
The limbic lobe of the cerebral cortex ...

functional-brain-systems-reticular-formation

Functional Brain Systems: Reticular Formation

The reticular formation is a complex network of gray and white matter spread across the core of the brainstem.
It is roughly divided into three paired ...

higher-mental-functions-of-brain-learning-and-memory

Higher Mental Functions of Brain: Learning and Memory

Memory is one of the most vital higher mental functions of the brain. Memory is closely related to learning because it enables us to retain information ...

higher-mental-functions-of-the-brain-language

Higher Mental Functions of the Brain: Language

Language is a system of communication that allows the expression of thoughts, ideas, and feelings. The brain processes language in both hemispheres.
...

Motor and Sensory Areas of the Cortex

The cerebral cortex has three functional areas &#8212; the motor, sensory, and association areas.
The motor areas, located in the frontal lobe, control ...

d. Obtain, evaluate, and summarize scientific findings regarding the biological origin of emotions and memories in distinct regions of the brain. Examples: the role of the frontal lobe in emotional regulation, the regulation of fear response by the amygdala

9-12.HA.1.5.d

Lungs, Airways, and Gas Exchange

Description

Transcript

Tags

More videos by Standards