Lecture 5: Abdominal Layers PDF

🐣 Lecture 5: Abdominal layers Abdominal Viscera (eg. stomach, small intestine, liver) are NOT in the peritoneal cavity - the peritoneal layer line these viscera and the abdominal cavity / peritoneal cavity...

🐣 Lecture 5: Abdominal layers Abdominal Viscera (eg. stomach, small intestine, liver) are NOT in the peritoneal cavity - the peritoneal layer line these viscera and the abdominal cavity / peritoneal cavity Peritoneal fluid is the predominant material in the peritoneal cavity → help things move, allowing for the flexibility of the structures in this area needed, for instance, for pregnancy or for digestion with peristalsis The peritoneum lines this cavity. The peritoneum lines both the body wall and the viscera The portion lining the body wall = parietal peritoneum Portion covering the organs = visceral peritoneum The parietal peritoneum and visceral peritoneum are one continuous sheet that prevents these structures from truly being within the peritoneal cavity Lecture 5: Abdominal layers 1  Peritoneal folds define the spaces in this abdominal cavity In the diagram, the peritoneal cavity is coloured in black In the diagram, on the right side, the shiny yellow area (scrawled in black) → peritoneum is clear, but the fatty tissue layer covered by the peritoneum - so most of the peritoneum reflects back on the body wall; this all this yellow layer is parietal peritoneum. Take home message: peritoneum lines all visceral organs and connects back to the body wall Lecture 5: Abdominal layers 2  Development defines peritoneal relationships Dorsally, the amniotic cavity & ventrally, the yolk SAC → which will eventually pinch off to form our gut too The amniotic cavity takes on fluid, causing it to flex laterally, we start to push in Pinching off this yolk SAC and create the future peritoneal cavity. Finally, we form one continuous layer developed during lateral folding, so lateral folding plays a critical role in forming the peritoneal space and defining the layers of peritoneum, the visceral or parietal layers. Peritoneum is a single layer that lines the body wall & the gut tube The body wall (both anterior and posterior) is lined with parietal peritoneum, and any gut tube derivatives are covered with visceral peritoneum Lecture 5: Abdominal layers 3  The gut tube extends from the oral cavity to the anal cavity In the foregut (extends both below and above the diaphragm), the peritoneum connects with both the anterior and posterior body wall Ventral and dorsal peritoneum In the midgut peritoneum connects only posteriorly Just dorsal peritoneum Connection between the parietal and visceral peritoneum are mesentery / ligaments Mesenteries are really important for conveying the neurovascular (from aorta to gut tube) Lecture 5: Abdominal layers 4  Defining Peritoneal Relationships Intraperitoneal, retroperitoneal, secondarily retroperitoneal Intraperitoneal: Organs that are intraperitoneal are completely surrounded by the peritoneum. These organs, such as the stomach, liver, and small intestine, are suspended within the abdominal cavity by mesenteries, allowing them to move freely within the peritoneal cavity. Retroperitoneal: Retroperitoneal organs lie behind the peritoneum, meaning they are only partially covered by it on their anterior side, with Lecture 5: Abdominal layers 5  the posterior side against the abdominal wall. Examples include the kidneys, adrenal glands, and the pancreas (except for its tail). These organs are more fixed in position compared to intraperitoneal organs. Secondarily Retroperitoneal: These organs initially develop as intraperitoneal organs but later become retroperitoneal during development as they lose their mesentery and become fixed to the posterior abdominal wall. Examples include the ascending and descending colon, and parts of the duodenum and pancreas. Diagram Lecture 5: Abdominal layers 6  Skin - in blue, deep to the skin, we have superficial fascia (fluffiness) Abdominal muscle layer - in red Our muscle layer is also lined with deep fascia. So we'll call this muscle and deep fascia. Peritoneal layer - in green Aorta needs to get important vessels to the gut tube to vascularise it - this vessel here would be the celiac trunk branches Take home message: Peritoneum conveys essential neurovascular supply Continue this layer Lecture 5: Abdominal layers 7  Be able to label this diagram Lecture 5: Abdominal layers 8 Lecture 5: Abdominal layers 9