Alright. We now want to look at the gross anatomy of the small intestine, and it's very likely you're going to be responsible for these three different sections of the small intestine. So that's what we're going to talk about. Now the regions of the small intestine. So we're just going to start out by saying that there are 3 sections of the small intestine, and in order they are the duodenum, the jejunum, and the ileum. And we can look over our image here. We have them labeled and color coded. You can see here in blue. That's going to be the duodenum. B in purple. That's all the jejunum. And C in this teal color. That is the ileum. Alright. So let's go through these one by one and see what we're talking about. So the duodenum, well that's that first section. We're going to say that this is the shortest section and it's just this sort of short C curve shaped section, and it's only about 10 centimeters long. Ten centimeters, that's something like 4 inches long. So we can see it in our image here coming right off the stomach off that pyloric sphincter valve. This sort of C curve there labeled A. That's going to be the duodenum. Now, in there are going to be some glands that are only present in the duodenum, and they are aptly named the duodenal glands. And the duodenal glands release an alkaline mucus. So remember the chyme coming from the stomach, it's going to have a very low pH. So you want an alkaline mucus to protect the wall of that duodenum, just like you had in the stomach, protecting the wall of the stomach. Now also coming into the duodenum, well remember we identified before the major duodenal papilla, that and that's where the pancreatic juice and the bile are going to come in. Now because you have the chyme, and the pancreatic juice, and the bile all coming in, that means we can sort of think of this as the mixing bowl of the intestine. It gets mixed in the duodenum and then it's going to move on to the jejunum. Alright. So the jejunum, again, that's that second region here in purple. And we're going to say that this is the middle section, and we mean middle both it's in between the other ones, but it's also sort of middle in terms of length. It's going to be 2 and a half meters, roughly. And 2 and a half meters is something somewhere around, like, 8 feet long. So it's a good size. Now the jejunum is going to be the site of most digestion and absorption. And when you think of the job of the small intestine, it is digestion and absorption. And so the jejunum is really doing most of that role. Alright. The kind that passes through the jejunum though is going to end up in the ileum, and the ileum is this third section down here labeled C. Now this is the 3rd section. It's also the longest section. Longest. Got to spell it right there. The longest section is something like over 3 and a half meters long, so something like 12 more feet of intestine there. And in the ileum, it's the longest section, but it's actually doing less than the jejunum. So it's going to absorb bile salts. So remember, bile entered into the duodenum. Now in the ileum, we're going to start picking up some of those bile salts so that they can be recycled and we can use them again. Now even more bile salts will get picked up in a large intestine later on. It's also going to absorb any remaining nutrients, but by this point there isn't a lot of nutrient left in the kind because most of it was absorbed in the jejunum. Alright. At the end of the ileum, we reach the ileocecal valve, and that's sort of right in here, on our image there. This is that sphincter separating the ileum from the cecum of the large intestine. The cecum is really that, sort of, the first section of that large intestine right there on our image. Alright. And the ileocecal valve, we can look at that word. It is the valve between the ileum and the cecum. Alright. So those are your major regions. Now I'll be honest, I get these regions switched in my head all the time, and so we have a little memory tool to keep it straight for you. I say DJ ileum feels the peristaltic pumps. Alright. Peristalsis, remember that's that wave of muscle contraction that's going to move chyme through the small intestine, and DJ ileum well, DJ that's the duodenum, the jejunum, and the ileum. Alright. There you go. We're going to look at this small intestine. Go inside and look at it in more detail. That's going to be coming up. But before that, we've got examples and practice. 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
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- 4. Tissues & Histology10h 3m
- Introduction to Tissues & Histology16m
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- 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
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- Specialized Connective Tissue: Cartilage44m
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- Introduction to Muscle Tissue7m
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- Nervous Tissue: The Neuron8m
- 5. Integumentary System2h 20m
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- An Introduction to Bone and Skeletal Tissue18m
- Gross Anatomy of Bone: Compact and Spongy Bone7m
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- Gross Anatomy of Bones - Structure of a Long Bone23m
- Microscopic Anatomy of Bones - Bone Matrix9m
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- Microscopic Anatomy of Bones - Trabeculae9m
- 7. The Skeletal System2h 35m
- 8. Joints2h 17m
- 9. Muscle Tissue2h 33m
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- 11. Nervous Tissue and Nervous System1h 35m
- 12. The Central Nervous System1h 6m
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- Introduction to the Peripheral Nervous System5m
- Organization of Sensory Pathways16m
- Introduction to Sensory Receptors5m
- Sensory Receptor Classification by Modality6m
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- 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
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- Introduction to Cells of the Immune System15m
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- Cells of the Immune System: Agranulocytes26m
- Introduction to Cell Communication5m
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- Introduction to the Complement System24m
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- Phagocytosis17m
- Introduction to Inflammation18m
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- Fever8m
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- Review Map of Innate Immunity
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- Antigens12m
- Introduction to T Lymphocytes38m
- Major Histocompatibility Complex Molecules20m
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- 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
23. The Digestive System
Small Intestine
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