We've been talking about how by changing the size of the thoracic cavity, we alter pressure gradients, and that forces air in and out of the lungs. But now we need to talk some anatomy and talk about how we actually change the size of that thoracic cavity, and that's going to be by using the muscles of ventilation. And so here, we're going to break those muscles of ventilation into 2 basic groups to start. We're going to talk about the primary respiratory muscles and the accessory respiratory muscles. So the primary respiratory muscles, these are going to be used during quiet breathing or what we call eupnea. And remember, quiet breathing or eupnea, that's that just sort of normal restful breathing where you use muscles for inspiration, but expiration is just the relaxation of muscles. And then accessory respiratory muscles, these are going to be recruited during forced breathing. Now for forced breathing, you're going to use both those primary respiratory muscles and the accessory respiratory muscles. But those accessory respiratory muscles are going to let you take those deeper, harder breaths in where you're using muscles for inspiration and muscular contraction for expiration. Alright. So let's take a look here. So we have 2 anatomical models, one for inspiration on the left, one for expiration on the right. Now for both of these right now, we just have the diaphragm drawn in. But as we go in, we'll be adding more muscles and highlighting them as we go. Alright. So we're going to start with inspiration, and we'll start with those primary respiratory muscles for inspiration. Well, the main one is that diaphragm. So I'm going to highlight that there in pink. And so for inspiration, that diaphragm contracts and it moves down. So you can see that diaphragm as it contracts, it pulls downwards, it sort of flattens out, straightens out, and that makes that space above the diaphragm in that thoracic cavity larger. Alright. Our other muscles that are doing work as part of the primary respiratory muscles that we'll draw in now, these are the external intercostals. The external intercostals, I'll highlight there in blue, and these are muscles that are linking between all your ribs. And you can see on the drawing, the muscle fibers actually connect the ribs and they slant sort of downwards and forwards. So as these contract, we're going to say the ribs move up and out. It's because your ribs are attached almost like hinges. So as they get sort of pulled up by these external intercostals, they sort of just hinge outwards a little bit, and that gives your chest sort of a rounder, more barrel-chested look when you breathe in. It's those intercostal muscles sort of making that rib cage bigger and rounder. And you can even see that on these diagrams, though it's subtle. You can see the one on the left. The rib cage looks a little bit more barrel-chested, a little bit rounder, and those ribs look a little just a little bit more parallel to the ground, whereas on a diagram on the right, they look like they're just pointing downwards just a little bit more. Alright. So that's the primary respiratory muscles, but what if you want to take a deeper breath? Well, we'll start by adding 2 muscles in here that are in the neck. We have the sternocleidomastoid, which I'm highlighting there in blue, and the scalenes, which I'm highlighting there in pink. So both these muscles are in the neck. This is your sternocleidomastoid here. It attaches to your clavicle. Your scalenes are on the side. They attach to the first and second ribs. And if you take a real deep breath, one thing that you'll notice if you're touching your neck is that your neck starts to flex. And what's happening there is that those muscles are pulling up on that rib cage because if you can lift the entire rib cage up while your diaphragm pulls down, that's going to create more room inside that thoracic cavity and it's going to let more air get in. Alright. We're going to have some more muscles that we'll layer on next here. We have the pectoralis minor and the serratus anterior. Pectoralis minor, I've highlighted there in pink. The serratus anterior, I've highlighted there in light blue. Now both these muscles attach to the scapula in your back, and they attach to the ribs in the front. So when these contract, they're going to pull back on that rib cage. And again, if you take a really deep breath, you'll probably feel yourself sort squeezing those shoulders back together. That's pulling that scapula back so that these muscles can lift up and pull that rib cage up and higher, and get more space inside that rib cage, just like that. Alright. Now as just a quick little memory tool for these, sometimes I would say that, for inspiration, we scale up the size of our rib cage. We scale up. And that word 'scale up', well, scale reminds me of the scalenes, but also those other muscles, sternocleidomastoid, scalenes, and serratus anterior. They all start with s's, so I remember my s muscles. And then the other one is our pectoralis minor there, and the p and up reminds me of that. So we scale up our rib cage. We lift it up to get as much space in there as we can. Alright. Well, what about expiration? Well, for expiration, our primary respiratory muscles, remember, these are just going to relax and allow recoil to force the air out. So our diaphragm, which we'll highlight there in pink, is going to relax, and then it is going to move up. Well, it moves up. Switch my pen back to blue here. It moves up, and you can see the shape of it. It's much more sort of rounded there, pushing up into the thoracic cavity, making less space inside that rib cage. Well, we can draw on our external intercostals here. These highlight in light blue. These are going to relax, and as they stop pulling up on those ribs, well, that means that the ribs then move down and they move in. They sort of just hinge backward down, making your rib cage sort of flatter again, making less space inside that thoracic cavity. Okay. Those muscles, though, those were just, remember, relaxing. Now let's talk about if you want to do forced breathing and really force air out with muscular contraction, we're going to use these accessory respiratory muscles. So I'm going to clear out these muscles and start anew so that we can see what we're looking at. And the first ones we're going to add on here are the internal intercostal muscles. Now just like these sound, these are just right underneath those external intercostal muscles, and I'll highlight them there in pink. So these are, again, connecting the ribs. But if you look closely, you'll see that the fibers are oriented in a different direction. They're connecting to the ribs, but they sort of go downwards and back. So when these contract, instead of hinging those ribs up and out, they hinge them down and in and flatten that rib cage even more. Alright. We also have a muscle here called the transversus thoracis, which I've highlighted in blue, and that's right underneath your sternum. And when that contracts, that pulls in and sort of collapses that rib cage, collapses those ribs in again, causing less space inside that thoracic cavity. And the final muscle we'll talk about here, I've drawn now, is that rectus abdominis, that major muscle of the abdomen. So we have this now highlighted in pink, and when that contracts, that squeezes inwards and that pushes on all the internal organs in your abdomen, and it sort of pushes them inwards, and they gotta go somewhere. And they just sort of push inwards and even up into that diaphragm, up into that thoracic cavity a little bit. So here, you're sort of collapsing your rib cage, bringing it downwards, and forcing organs sort of upwards into your thoracic cavity, forcing air out of your lungs. Right? So we can do the whole thing. Right? We'll take a deep breath in. You'll feel that rib cage get really big. You'll feel yourself lift up and pull back on it. And then through expiration, you'll feel yourself pulling down, collapsing inwards, pushing in on those organs so they go up into your thoracic cavity, forcing air out. So breathe in, breathe out. Alright. So those are the muscles of inspiration and the muscles of expiration. We'll practice some more and practice problems to come. I'll see you there.
Table of contents
- 1. Introduction to Anatomy & Physiology5h 40m
- What is Anatomy & Physiology?20m
- Levels of Organization13m
- Variation in Anatomy & Physiology12m
- Introduction to Organ Systems27m
- Homeostasis9m
- Feedback Loops11m
- Feedback Loops: Negative Feedback19m
- Feedback Loops: Positive Feedback11m
- Anatomical Position7m
- Introduction to Directional Terms3m
- Directional Terms: Up and Down9m
- Directional Terms: Front and Back6m
- Directional Terms: Body Sides12m
- Directional Terms: Limbs6m
- Directional Terms: Depth Within the Body4m
- Introduction to Anatomical Terms for Body Regions3m
- Anatomical Terms for the Head and Neck8m
- Anatomical Terms for the Front of the Trunk8m
- Anatomical Terms for the Back9m
- Anatomical Terms for the Arm and Hand9m
- Anatomical Terms for the Leg and Foot15m
- Review- Using Anatomical Terms and Directions12m
- Abdominopelvic Quadrants and Regions19m
- Anatomical Planes & Sections17m
- Organization of the Body: Body Cavities13m
- Organization of the Body: Serous Membranes14m
- Organization of the Body: Serous Membrane Locations8m
- Organization of the Body: Thoracic Cavity8m
- Organization of the Body: Abdominopelvic Cavity12m
- 2. Cell Chemistry & Cell Components12h 37m
- Atoms- Smallest Unit of Matter57m
- Isotopes39m
- Introduction to Chemical Bonding19m
- Covalent Bonds40m
- Noncovalent Bonds5m
- Ionic Bonding37m
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- Introduction to Water7m
- Properties of Water- Cohesion and Adhesion7m
- Properties of Water- Density8m
- Properties of Water- Thermal14m
- Properties of Water- The Universal Solvent17m
- Acids and Bases12m
- pH Scale21m
- Carbon8m
- Functional Groups9m
- Introduction to Biomolecules2m
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- Carbohydrates23m
- Proteins25m
- Nucleic Acids34m
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- Microscopes10m
- Prokaryotic & Eukaryotic Cells26m
- Introduction to Eukaryotic Organelles16m
- Endomembrane System: Protein Secretion34m
- Endomembrane System: Digestive Organelles15m
- Mitochondria & Chloroplasts21m
- Endosymbiotic Theory10m
- Introduction to the Cytoskeleton10m
- Cell Junctions8m
- Biological Membranes10m
- Types of Membrane Proteins7m
- Concentration Gradients and Diffusion9m
- Introduction to Membrane Transport14m
- Passive vs. Active Transport13m
- Osmosis33m
- Simple and Facilitated Diffusion17m
- Active Transport30m
- Endocytosis and Exocytosis15m
- 3. Energy & Cell Processes10h 7m
- Introduction to Energy15m
- Laws of Thermodynamics15m
- Chemical Reactions9m
- ATP20m
- Enzymes14m
- Enzyme Activation Energy9m
- Enzyme Binding Factors9m
- Enzyme Inhibition10m
- Introduction to Metabolism8m
- Redox Reactions15m
- Introduction to Cellular Respiration22m
- Types of Phosphorylation11m
- Glycolysis19m
- Pyruvate Oxidation8m
- Krebs Cycle16m
- Electron Transport Chain14m
- Chemiosmosis7m
- Review of Aerobic Cellular Respiration19m
- Fermentation & Anaerobic Respiration23m
- Introduction to Cell Division22m
- Organization of DNA in the Cell17m
- Introduction to the Cell Cycle7m
- Interphase18m
- Phases of Mitosis48m
- Cytokinesis16m
- Cell Cycle Regulation18m
- Review of the Cell Cycle7m
- Cancer13m
- Introduction to DNA Replication22m
- DNA Repair7m
- Central Dogma7m
- Introduction to Transcription20m
- Steps of Transcription19m
- Genetic Code25m
- Introduction to Translation30m
- Steps of Translation23m
- Post-Translational Modification6m
- 4. Tissues & Histology10h 3m
- Introduction to Tissues & Histology16m
- Introduction to Epithelial Tissue24m
- Characteristics of Epithelial Tissue37m
- Structural Naming of Epithelial Tissue19m
- Simple Epithelial Tissues1h 2m
- Stratified Epithelial Tissues55m
- Identifying Types of Epithelial Tissue32m
- Glandular Epithelial Tissue26m
- Introduction to Connective Tissue36m
- Classes of Connective Tissue8m
- Introduction to Connective Tissue Proper40m
- Connective Tissue Proper: Loose Connective Tissue56m
- Connective Tissue Proper: Dense Connective Tissue49m
- Specialized Connective Tissue: Cartilage44m
- Specialized Connective Tissue: Bone12m
- Specialized Connective Tissue: Blood9m
- Introduction to Muscle Tissue7m
- Types of Muscle Tissue45m
- Introduction to Nervous Tissue8m
- Nervous Tissue: The Neuron8m
- 5. Integumentary System2h 20m
- 6. Bones & Skeletal Tissue2h 16m
- An Introduction to Bone and Skeletal Tissue18m
- Gross Anatomy of Bone: Compact and Spongy Bone7m
- Gross Anatomy of Bone: Periosteum and Endosteum11m
- Gross Anatomy of Bone: Bone Marrow8m
- Gross Anatomy of Bone: Short, Flat, and Irregular Bones5m
- Gross Anatomy of Bones - Structure of a Long Bone23m
- Microscopic Anatomy of Bones - Bone Matrix9m
- Microscopic Anatomy of Bones - Bone Cells25m
- Microscopic Anatomy of Bones - The Osteon17m
- Microscopic Anatomy of Bones - Trabeculae9m
- 7. The Skeletal System2h 35m
- 8. Joints2h 17m
- 9. Muscle Tissue2h 33m
- 10. Muscles1h 11m
- 11. Nervous Tissue and Nervous System1h 35m
- 12. The Central Nervous System1h 6m
- 13. The Peripheral Nervous System1h 26m
- Introduction to the Peripheral Nervous System5m
- Organization of Sensory Pathways16m
- Introduction to Sensory Receptors5m
- Sensory Receptor Classification by Modality6m
- Sensory Receptor Classification by Location8m
- Proprioceptors7m
- Adaptation of Sensory Receptors8m
- Introduction to Reflex Arcs13m
- Reflex Arcs15m
- 14. The Autonomic Nervous System1h 38m
- 15. The Special Senses2h 41m
- 16. The Endocrine System2h 48m
- 17. The Blood1h 22m
- 18. The Heart1h 42m
- 19. The Blood Vessels3h 35m
- 20. The Lymphatic System3h 16m
- 21. The Immune System14h 37m
- Introduction to the Immune System10m
- Introduction to Innate Immunity17m
- Introduction to First-Line Defenses5m
- Physical Barriers in First-Line Defenses: Skin13m
- Physical Barriers in First-Line Defenses: Mucous Membrane9m
- First-Line Defenses: Chemical Barriers24m
- First-Line Defenses: Normal Microbiota7m
- Introduction to Cells of the Immune System15m
- Cells of the Immune System: Granulocytes28m
- Cells of the Immune System: Agranulocytes26m
- Introduction to Cell Communication5m
- Cell Communication: Surface Receptors & Adhesion Molecules16m
- Cell Communication: Cytokines27m
- Pattern Recognition Receptors (PRRs)48m
- Introduction to the Complement System24m
- Activation Pathways of the Complement System23m
- Effects of the Complement System23m
- Review of the Complement System13m
- Phagocytosis17m
- Introduction to Inflammation18m
- Steps of the Inflammatory Response28m
- Fever8m
- Interferon Response25m
- Review Map of Innate Immunity
- Introduction to Adaptive Immunity32m
- Antigens12m
- Introduction to T Lymphocytes38m
- Major Histocompatibility Complex Molecules20m
- Activation of T Lymphocytes21m
- Functions of T Lymphocytes25m
- Review of Cytotoxic vs Helper T Cells13m
- Introduction to B Lymphocytes27m
- Antibodies14m
- Classes of Antibodies35m
- Outcomes of Antibody Binding to Antigen15m
- T Dependent & T Independent Antigens21m
- Clonal Selection20m
- Antibody Class Switching17m
- Affinity Maturation14m
- Primary and Secondary Response of Adaptive Immunity21m
- Immune Tolerance28m
- Regulatory T Cells10m
- Natural Killer Cells16m
- Review of Adaptive Immunity25m
- 22. The Respiratory System3h 20m
- 23. The Digestive System2h 5m
- 24. Metabolism and Nutrition4h 0m
- Essential Amino Acids5m
- Lipid Vitamins19m
- Cellular Respiration: Redox Reactions15m
- Introduction to Cellular Respiration22m
- Cellular Respiration: Types of Phosphorylation14m
- Cellular Respiration: Glycolysis19m
- Cellular Respiration: Pyruvate Oxidation8m
- Cellular Respiration: Krebs Cycle16m
- Cellular Respiration: Electron Transport Chain14m
- Cellular Respiration: Chemiosmosis7m
- Review of Aerobic Cellular Respiration18m
- Fermentation & Anaerobic Respiration23m
- Gluconeogenesis16m
- Fatty Acid Oxidation20m
- Amino Acid Oxidation17m
- 25. The Urinary System2h 39m
- 26. Fluid and Electrolyte Balance, Acid Base Balance Coming soon
- 27. The Reproductive System2h 5m
- 28. Human Development1h 21m
- 29. Heredity Coming soon
22. The Respiratory System
Ventilation
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