Stomach Anatomy, Parts, Names & Diagram

Stomach Anatomy: Complete Guide with Parts, Names, Functions & Diagram

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Overview of Stomach Anatomy

The stomach is a hollow, muscular organ located in the upper part of the digestive system, between the esophagus and the small intestine. It plays a critical role in breaking down food. It uses gastric acid and digestive enzymes to chemically process food after it has been chewed and swallowed. This process follows the cephalic phase, which begins with the sight, smell, or thought of food. The stomach anatomy consists of four main sections and two curvatures. It gets its blood supply primarily from the celiac trunk. At the same time, its nerve signals come from the vagus nerves and the celiac plexus. In this article, we’ll explore the stomach anatomy, its internal and external parts, and how its blood and nerves work together.

Stomach Anatomy Diagram

Stomach Anatomy, Parts, Names & Diagram

Anatomy of the Stomach

External Stomach Anatomy

  1. Regions of the Stomach:
    • Cardia
    • Fundus
    • Body (Corpus)
      • Pylorus
        • Antrum
        • Pyloric canal
      • Pyloric sphincter
  2. Curvatures:
    • Lesser curvature
    • Greater curvature
  3. Surfaces:
    • Anterior surface
    • Posterior surface

Internal Stomach Anatomy

  1. Layers of the Stomach Wall:
    • Mucosa
    • Submucosa
    • Muscularis externa
      • Inner oblique layer
      • Middle circular layer
      • Outer longitudinal layer
    • Serosa
  2. Gastric Glands
    • Cardiac Glands
    • Fundic Glands
    • Pyloric Glands
  3. Rugae:

Blood Supply

  • Arterial supply:
    • Left gastric artery
    • Right gastric artery
    • Right gastroepiploic artery
    • Left gastroepiploic artery
    • Short gastric arteries
  • Venous drainage:

Nerve Supply

  • Parasympathetic
  • Sympathetic

Lymphatic Drainage

External Stomach Anatomy

The stomach is located in the upper abdomen, mostly under the lower ribs on the left side. Its lower portion extends toward the middle of the abdomen, in the epigastric and upper umbilical areas.

The stomach is connected to nearby organs like the liver, spleen, diaphragm, and transverse colon through supportive ligaments. The external anatomy of the stomach includes distinct regions, curvatures, and surfaces, each contributing to its structure and function.

Regions of the Stomach

Your stomach is divided into five distinct sections, each with a specific function:

  • Cardia: It is the entry point where food passes from the esophagus into the stomach. A muscular valve, the cardiac sphincter, prevents food and stomach acid from flowing upward.
  • Fundus: Positioned near the diaphragm, this dome-shaped section stores undigested food and releases gases produced during digestion.
  • Body (Corpus): The central and largest part of the stomach, it churns food and mixes it with digestive juices to begin the breakdown process.
  • Antrum: Located below the body, this region temporarily holds partially digested food, preparing it for transfer to the next stage of digestion.
  • Pyloric: The pyloric region forms the stomach’s exit, channeling its contents into the duodenum. This section consists of the pyloric antrum, which connects to the main body of the stomach, and the pyloric canal, leading directly to the duodenum. The transition is regulated by the pyloric orifice, an opening controlled by the pyloric sphincter.
  • Pyloric Sphincter: It is a ring of smooth muscle that manages the flow of partially digested food into the small intestine.

Curvatures

The stomach’s medial and lateral edges are shaped into two distinct curves: the lesser curvature and the greater curvature.

  • Greater Curvature: This longer, outward curve defines the stomach’s lateral edge. It starts at the cardiac notch, sweeps back, descends to the left, and curves rightward to meet the pyloric antrum. Blood supply to this curvature comes from the short gastric arteries and the right and left gastro-omental arteries, ensuring nourishment to its structures.
  • Lesser Curvature: The short and inward curve forms the stomach’s medial border. Its lowest point, called the angular notch, marks the transition between the stomach’s body and the pyloric region. The lesser curvature anchors the hepatogastric ligament and is supplied by the left gastric artery and a branch from the hepatic artery.

Omentum

The greater and lesser omenta are double-layered folds of the peritoneum that play critical roles in abdominal structure and function. Both are attached to the stomach and serve as key anatomical landmarks:

  • Greater Omentum: It extends from the greater curvature of the stomach. This large, sheet-like structure drapes over the intestines before folding back to attach to the transverse colon. It houses numerous lymph nodes, which play a vital role in immune defense by containing infections and reducing inflammation within the abdominal cavity.
  • Lesser Omentum: This smaller, thinner fold links the stomach’s lesser curvature and the upper duodenum to the liver. It acts as a support structure, ensuring the stability of these organs while maintaining essential connections between them.

Surfaces

  • Anterior Surface: The front of the stomach lies in contact with the left lobe of the liver (segments II, III, and IV), the abdominal wall, and the distal part of the transverse colon.
  • Posterior Surface: Its back surface rests against the left diaphragm, spleen, left kidney, adrenal gland, and pancreas. Together, these structures form the “stomach bed,” providing support and defining its anatomical relationships.

Internal Stomach Anatomy

The stomach’s internal structure consists of five distinct regions, layers forming its wall, and specialized folds lining its interior.

Layers of the Stomach Wall

The stomach is made up of four distinct layers, each with a specialized role in digestion: the mucosa, submucosa, muscularis externa, and serosa.

  • Mucosa (Inner Layer): This innermost lining contains glands that produce mucus, digestive enzymes, and stomach acid. These secretions protect the stomach and aid in breaking down food. When the stomach is empty, the mucosa folds into ridges called rugae, which flatten as the stomach fills, allowing it to expand.
  • Submucosa: It is situated beneath the mucosa. This connective tissue layer houses blood vessels, lymphatic vessels, and nerves. It supports the mucosa and ensures a steady supply of nutrients and oxygen while aiding in the stomach’s coordination and response to stimuli.
  • Muscularis Externa: This muscular layer drives the stomach’s mechanical digestion through three distinct muscle types:
    • The inner oblique layer is unique to the stomach, and churns and kneads food into a semi-liquid mixture.
    • The middle circular layer forms the pyloric sphincter, regulating food passage into the small intestine.
    • The outer longitudinal layer facilitates coordinated contractions, helping move and mix the stomach’s contents.
  • Serosa (Outer Layer): The serosa, also known as the visceral peritoneum, is a smooth outer covering that shields the stomach and minimizes friction with surrounding organs. It anchors the stomach securely within the abdominal cavity. This multi-layered structure enables the stomach to digest food effectively. It combines mechanical and chemical processes while protecting and maintaining its functional integrity.

Gastric Glands

The gastric glands are tiny, tube-like structures found in the inner lining of the stomach. These glands are essential for digestion, as they produce various substances needed to break down food.

They start at small openings in the stomach lining called gastric pits, which are part of the stomach’s mucous layer. The gastric pits contain cells that release mucus to protect the stomach lining. Below the pits, the glands extend deeper and are divided into parts called the isthmus and neck.

Most gastric glands work as exocrine glands, meaning they release their secretions like gastric juices and mucus into the stomach to aid digestion and protect it from damage. Below are some types of gastric glands explained in detail.

1. Cardiac Glands

Cardiac glands are located near the stomach’s cardiac opening. They are relatively few and reside within the shallow layers of the mucosa. These glands occur in two forms: simple tubular glands, resembling those in the pyloric region, and compound racemose glands, similar to duodenal glands.

Their main function is to produce mucus, which protects the stomach lining from acidic damage and ensures smooth food movement through the digestive tract.

2. Fundic Glands

Fundic glands are found in the stomach’s fundus and body. They are straight, tubular structures that often share a common duct. These glands occupy about one-sixth of their total length with secretory tubes and are shorter than pyloric glands.

They are lined with columnar epithelial cells and play a crucial role in digestion by secreting pepsinogen (a precursor to the enzyme pepsin) and hydrochloric acid (HCl). Together, these substances break down proteins and maintain the acidic environment needed for digestion.

3. Pyloric Glands

Pyloric glands are situated in the pyloric region. These glands are primarily endocrine and consist of two or three coiled tubes merging into a shared duct. The ducts are lined with columnar cells, while the tubes are formed of granular cuboidal cells.

These glands produce mucus to protect the stomach lining and gastrin, a hormone G cells release. Gastrin regulates gastric acid secretion, promoting efficient digestion and coordinating stomach motility.

Rugae

Rugae are found in the mucosal and submucosal layers of the stomach. They are specialized structures that enable the stomach to stretch and accommodate food.

These rugae also called gastric folds, play a vital role in maintaining the stomach’s elasticity. When food enters, mechanoreceptors detect the rising pressure, triggering the folds to flatten and expand the stomach’s capacity without significantly increasing internal pressure.

This adaptive mechanism not only allows for efficient storage but also increases the surface area available for digestion and nutrient absorption. Gastric folds are often visible during procedures like esophagogastroduodenoscopy or in imaging studies.

Blood Supply

The stomach gets most of its blood from the abdominal aorta, with two main systems working together along its curves, along with some direct branches.

  • Lesser Curvature: Blood is supplied by an artery from the common hepatic artery (right gastric) and another from the celiac trunk (left gastric). These arteries connect to form a network.
  • Greater Curvature: The right and left gastroomental (or gastroepiploic) arteries provide blood here. The right comes from the gastroduodenal artery, and the left comes from the splenic artery.
  • Fundus and Upper Body: Blood comes from short and posterior gastric arteries, which are branches of the splenic artery.
  • Pylorus: Blood is supplied by the gastroduodenal artery, a branch of the common hepatic artery.

The veins in the stomach follow the same pattern as the arteries and drain into three main vessels: the hepatic portal vein, the splenic vein, and the superior mesenteric vein.

Nerve Supply

The stomach’s nerve supply is managed by the autonomic nervous system, divided into two key branches:

  • Parasympathetic Nerves: These arise from the vagus nerve, specifically its anterior and posterior vagal trunks. They play a crucial role in digestion by enhancing stomach functions, such as increasing muscle contractions and promoting the secretion of digestive enzymes.
  • Sympathetic Nerves: Originating from spinal segments T6 to T9, these nerves travel to the stomach via the greater splanchnic nerve and the coeliac plexus. They inhibit digestion by reducing stomach activity and also transmit pain signals to the brain.

Read More-

Lower Limb

Upper Limb

Human Head

Organs

External Sources-

  • Wikipedia
  • KenHub
  • Optometrists
  • Cleveland Clinic
  • American Academy of Ophthalmology

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