:   / drgbhanuprakash  
: https://t.me/bhanuprakashdr
: https://linktr.ee/DrGBhanuprakash

Anatomy of Ileum Animation: Blood supply, Venous drainage, Histology, Innervation, Functions

Definition

The ileum is the third and final part of the small intestine. It follows the duodenum and the jejunum and leads into the cecum, which is the first part of the large intestine. The ileum is typically between 3.5 and 4 meters long and its primary role is to absorb nutrients and salts that were not absorbed by the jejunum.

Blood Supply

The ileum receives its blood supply primarily from the ileal branches of the superior mesenteric artery. These are called the straight arteries or arteriae rectae. The blood flows into the small intestine through a series of progressively smaller vessels known as arterial arcades, then finally reaching the straight arteries which supply the gut wall.

After oxygen and nutrients have been extracted from the blood, it is returned to the heart via the superior mesenteric vein. This vein drains directly into the portal vein, which carries the blood to the liver for further metabolism before it is returned to systemic circulation.

Innervation

The innervation of the ileum involves both the parasympathetic and sympathetic nervous systems. Parasympathetic innervation is mainly provided by the vagus nerve, which helps to stimulate peristalsis and secretory activities. The coeliac and superior mesenteric plexuses mainly provide sympathetic innervation, which generally has inhibitory effects, slowing peristalsis and reducing secretion.

Histology

The structure of the ileum, like other parts of the gastrointestinal tract, is divided into several layers:

Mucosa: This innermost layer comes into direct contact with digested food (chyme). It's made up of simple columnar epithelium, which has many folds and projections (villi and microvilli) to increase surface area for better nutrient absorption. The ileum is distinctive for its numerous aggregated lymphoid follicles, known as Peyer's patches, which play a significant role in immune response.

Submucosa: This layer is composed of dense connective tissue and contains blood vessels, lymphatic vessels, and nerves that help control the contraction and dilation of the ileum.

Muscularis: The muscularis is made up of two layers of smooth muscle (inner circular and outer longitudinal). These muscle layers contract in a rhythmic manner, propelling the food along the intestine (a process called peristalsis).

Serosa: The outermost layer, the serosa, is a layer of simple squamous epithelium which secretes a fluid to reduce friction with other organs in the abdomen, allowing the ileum to move smoothly during digestion.

Function

The primary functions of the ileum are the continuation of the digestion process and nutrient absorption, but it also has other specific roles:

Digestion and absorption: The ileum completes the process of enzymatic digestion initiated in the duodenum. It absorbs important nutrients like vitamin B12, bile salts, and any remaining products of digestion including carbohydrates, proteins, and lipids.

Immune function: Peyer's patches in the ileum form an important part of the immune system, protecting the body from harmful bacteria that might enter through the digestive tract.

Bile salts and vitamin B12 absorption: The ileum is also crucial in the reabsorption of bile salts, which are used for the digestion of dietary fats, and vitamin B12, which is essential for the formation of red blood cells and the functioning of the nervous system.

Ileocecal valve: At the junction of the ileum and the large intestine is the ileocecal valve, which prevents the backflow of colonic contents into the ileum.


#Ileum #Anatomy #SmallIntestine #DigestiveSystem #BloodSupply #Histology #Innervation #IleumFunction #Absorption #ImmuneSystem #NutrientAbsorption #HumanAnatomy #MedicalEducation #Medicine #Healthcare #Biology #Physiology #Gastroenterology #MedicalScience #LearningAnatomy #MedicalStudy #AnatomyAndPhysiology #fmge #fmgevideos #rapidrevisionfmge #fmgejan2023 #mbbslectures #nationalexitexam #nationalexittest #neetpg #usmlepreparation #usmlestep1 #fmge #usmle #drgbhanuprakash #medicalstudents #medicalstudent #medicalcollege #neetpg2023 #usmleprep #usmlevideos #usmlestep1videos #medicalstudents #neetpgvideos