Uploaded October 2021 | Updated September 2026, 1 week ago

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Content:
0:00 Introduction
0:40 Small Intestine Overview
1:14 Duodenum
3:39 Jejunum and Ileum
6:48 Anatomical Structures of the Duodenum
9:35 Anatomical Structures of Jejunum and Ileum
10:25 Layers of the Small Intestinal Wall

Small Intestine Overview:
- Small Intestine goes from the Pylorus to the Caecum
- Approx 7 meters long in adults
- Parts of the small intestine: Duodenum, Jejunum, Ileum

Duodenum:
- 20-30cm
- Responsible for Iron Absorbtion, Chemical Digestion, Chemical Neutralization
- Processes Chyme from the stomach

Topography of the Duodenum:
- Skeletopy: From L1 to L3
- Syntopy:
○ Behind Duodenum: Inferior Vena Cava, Aorta, Right Kidney
○ Above Duodenum: Liver, Pancreas
○ Anteriorly: Transverse Colon
- Holotopy: Epigastric Region and Umbilical Region

Jejunum and Ileum:
- No strict demarcation between jejunum and ileum
- Jejunum (2-3 meters long)
○ Primary Function: Absorbtion
- Ileum (2-4 meters long)
○ Absorbs remaining nutrients and vitamins (vitamin b12)

Topography of the Jejunum and Ileum:
- Skeletopy: L2 to Right Iliac Fossa
- Syntopy:
○ Surrounded by Caecum, Ascending colon, transverse colon, descending colon and sigmoid colon
○ Posteriorly: Fixated to posterior abdominal wall through the root of the mesentery (Radix Mesenterii)
○ Anteriorly: Greater Omentum
- Holotopy:
○ Ileum: Umbilical and left lateral region
○ Jejunum: Left Lateral Region, Right Inguinal Region, Pubic Region

Anatomical Structures:
- Duodenum:
○ Superior Part
§ from Pyloric Orifice (Ostium Pyloricum)
§ To Superior Duodenal Flexure (Flexura Duodeni Superior)
○ Descending Part
§ From Superior Duodenal Flexure (Flexura Duodeni Superior)
§ To Inferior Duodenal Flexure (Flexura Duodeni Inferior)
○ Inferior Horizontal Part
§ From Inferior Duodenal Flexure (Flexura Duodeni Inferior)
○ Ascending Part
§ Until Duodenojejunal Flexure (Flexura Duodenojejunalis) / Ligament of Treitz
- Jejunum:
○ Wider, Thicker than Ileum
○ More vascular
○ Darker in colour
- Ileum:
○ Thinner
○ Less Vascular
○ Lighter in Colour

Layers of the Small Intestinal Wall:
- Tunica Mucosa
○ Made up of Simple Columnar Epithelium
○ Circular Folds (Plicae Circulare) absent in the duodenal bulb (bulbus duodeni)
○ Intestinal Villi (Villi Intestinales)
○ Microvilli
○ Intestinal Glands (Glandula Intestinales)
○ Solitary Lymphoid Nodules (Noduli Lymphoidei Solitarii)
○ Aggregated lymph nodules (Noduli Lymphoidei Aggregati)
○ AT the duodenum:
§ Major Duodenal Papilla (Papilla Duodeni Major)
§ Minor Duodenal Papilla (Papilla Duodeni Minor)
- Tela Submucosa
○ Duodenum: Brunners Glands
○ Jejunum: Longer Villi
○ Ileum: More goblet cells in mucosa and has Peyers Patches (GALT)
- Tunica Muscularis
○ Provides Peristaltic movement (peristalsis)
○ Inner Layer: Circular Muscle Layer
§ Hepatopancreatic Sphincter (Sphincter of Oddi) (M. Sphincter Ampullae Hepatopancreatica)
○ Outer Layer: Longitudinal Muscle Layer
- Tunica Serosa
○ Intraperitoneal Organs (Peritoneum)
○ Retroperitoneal Organs (Duodenum) has tunica adventitia at some parts

Sources used in this video:
- Memorix Anatomy 2nd Edition by Hudák Radovan (Author), Kachlík David (Author), Volný Ondřej (Author)
- Biorender
- University notes and lectures