alevel biology

• What are the different layers of the ileum, working from the outside in?

  Serosa, muscularis externa, submucosa, muscularis mucosa, mucosa
• What is the role of the serosa layer in the ileum?

  It provides a thin protective and supportive lining for the alimentary canal
• What are the two layers of the muscularis externa in the ileum and what are their functions?

  Outer longitudinal muscle causes pendular movement, inner circular muscle causes local constrictions and peristaltic waves
• What is the main component of the submucosa layer in the ileum?

  Connective tissue
• What is the role of the muscularis mucosa layer in the ileum?

  It moves the villi to increase contact with digested food in the gut lumen
• What is the main feature of the mucosa layer in the ileum?

  It has a substantially increased surface area due to the presence of villi and microvilli
• What are the functions of the different layers of the ileum?

  • Serosa: Provides a protective and supportive lining
  • Muscularis externa:
  • Longitudinal muscle causes pendular movement
  • Circular muscle causes local constrictions and peristaltic waves
  • Submucosa: Contains blood and lymphatic vessels for absorption
  • Muscularis mucosa: Moves the villi to increase contact with digested food
  • Mucosa: Has increased surface area with villi and microvilli for absorption
• If you wanted to observe the detailed structure of the villi in the ileum, which type of microscope would you use?

  Scanning electron microscope (SEM)
• How do the contractions of the longitudinal and circular muscle layers in the muscularis externa work together to move food through the ileum?

  Contractions of the longitudinal muscle cause pendular movement, while contractions of the circular muscle cause local constrictions and peristaltic waves to push food along
• What is the relationship between the muscularis mucosa layer and the villi in the ileum?

  • The muscularis mucosa layer contains small strands of muscle that extend into the villi
  • Contractions of these muscle strands help produce the characteristic 'wafting' movement of the villi
  • This increased movement of the villi helps to increase contact with digested food in the gut lumen
• If you wanted to observe the detailed 3D surface structure of the ileum, which type of microscope would you use?

  Scanning electron microscope (SEM)
• What are the key differences between the functions of a scanning electron microscope (SEM) and a transmission electron microscope (TEM)?

  • SEMs produce 3D images, while TEMs produce 2D images
  • SEMs are used to study the surface structure of samples, while TEMs are used to study the internal structure of thin samples
  • SEMs use a focused beam of electrons to scan the surface, while TEMs use a beam of electrons that passes through the sample
• What is the formula to calculate the area of a circle with radius $r$?


  $A =$$\pi r^2$