Digestive System Notes - ANAT1052 Unit 9 PDF

**1. Define Alimentary Canal.** +-----------------------------------+-----------------------------------+ | **Term** | **Description** | +===================================+===================================+ | **Alimentary Canal** | -Also k...

**1. Define Alimentary Canal.** +-----------------------------------+-----------------------------------+ | **Term** | **Description** | +===================================+===================================+ | **Alimentary Canal** | -Also known as the **digestive | | | tract;** A **continuous tube | | | running from the | | | [mouth] to the | | | [anus]** | | | | | | *-Gastrointestinal tract: Stomach | | | and intestines (small and large)* | | | | | | **[Food passage]: | | | Mouth → Pharynx → Esophagus → | | | Stomach → Small Intestine → Large | | | Intestine → Rectum → Anus** | +-----------------------------------+-----------------------------------+ **Type** **Organs** ---------------------- ---------------------------------------------------------------------- **Main Organs** Mouth, pharynx, esophagus, stomach, small intestine, large intestine **Accessory Organs** Teeth, tongue, salivary glands, liver, gallbladder, pancreas. **2. and 3. Main and Accessory Organs of the Digestive System** **4. Three Processes of Food Ingestion** +-----------------------------------+-----------------------------------+ | **Process** | **Description** | +===================================+===================================+ | **Digestion** | -**Mechanical and chemical | | | breakdown of food** into a form | | | usable by the body; Begins in the | | | oral cavity with chewing and | | | salivary enzymes, continues in | | | the stomach with gastric acids, | | | and completes in the small | | | intestine with digestive enzymes | | | from the pancreas and bile from | | | the liver | | | | | | -**Mechanical digestion**: | | | physical breakdown of food into | | | smaller particles, achieved by | | | the cutting and grinding action | | | of the teeth and the churning | | | movements of the stomach; exposes | | | more food surface to the action | | | of the digestive enzymes | | | | | | -**Chemical digestion**: process | | | of breaking down food into | | | simpler, absorbable molecules | | | through the action of enzymes and | | | digestive juices; all chemical | | | digestion is by the process of | | | enzymatic hydrolysis, breaking | | | covalent bonds by adding water to | | | them; the digestive enzymes that | | | carry out enzymatic hydrolysis | | | are produced by the salivary | | | glands, stomach, pancreas, and | | | small intestine | +-----------------------------------+-----------------------------------+ | **Absorption** | \- Uptake of nutrient molecules | | | into the epithelial cells of the | | | digestive tract and then into the | | | blood or lymph (by **lacteals**) | | | | | | -Primarily occurs in the small | | | intestine | +-----------------------------------+-----------------------------------+ | **Metabolism** | **-Catabolism in Digestion**: The | | | digestive system initiates | | | catabolism by breaking down food | | | into basic nutrients. | | | | | | **-Cellular Respiration as a | | | Catabolic Process**: Nutrients | | | like glucose undergo cellular | | | respiration in the cells to | | | produce ATP, which supplies | | | energy. | | | | | | **-Anabolism for Growth and | | | Repair**: The energy produced | | | through cellular respiration is | | | also used for anabolic processes, | | | where the body builds and repairs | | | tissues. | | | | | | **-One way to measure metabolism, | | | particularly catabolism, is to | | | measure O₂ consumption**. The | | | rate of oxygen consumption | | | reflects the rate of ATP | | | production, which is largely | | | driven by catabolic processes | | | | | | -**Rate of O₂ use = rate of ATP | | | production**, as cells use oxygen | | | to generate ATP through cellular | | | respiration to meet energy | | | demands. | +-----------------------------------+-----------------------------------+ **5. Mouth: Location, Structure, and Function** +-----------------------------------+-----------------------------------+ | **Structure** | **Description** | +===================================+===================================+ | **Mouth** | **-**Opening between the lips; | | | entrance of the digestive tract | | | (anything behind the mouth is the | | | **oral cavity**) | +-----------------------------------+-----------------------------------+ | **Hard & Soft Palate** | -Palate is the roof of the oral | | | cavity, separating the oral | | | cavity from the nasal cavity | | | | | | -Hard palate: anterior portion; | | | reinforced by bone | | | | | | -Soft palate: posterior portion; | | | more spongy | +-----------------------------------+-----------------------------------+ | **Uvula** | -A fleshy, grape-like projection | | | hanging down from the soft | | *"little grape"* | palate, at the back of the throat | | | | | | **[Functions:]** | | | | | | -**Secretes Saliva**: Assists in | | | keeping the throat moist and | | | helps with swallowing. | | | | | | -**Deflects Food and Liquid**: | | | Directs food and liquids | | | downward, preventing them from | | | entering the nasal passages. | | | | | | -**Seals the Nasal Passage:** | | | move upward to close off the | | | nasopharynx, preventing food from | | | entering the nasal cavity during | | | swallowing | | | | | | -**Assists with Sound and | | | Speech:** Helps produce certain | | | sounds and adds depth to speech. | +-----------------------------------+-----------------------------------+ | **Tongue** | -Made up of the tongue proper | | | (body of the tongue) and several | | | other muscles | | | | | | \- Large but not that large; | | | Supported by the hyoid bone: The | | | hyoid bone is a small, U-shaped | | | bone that \"floats\" above the | | | larynx and supports | | | | | | the tongue, though it doesn't | | | directly attach to other bones. | | | | | | \- Precise movements that prevent | | | biting: The tongue has remarkable | | | motor control, allowing us to eat | | | and speak without frequently | | | biting it | | | | | | **[Function:]** | | | | | | -Moves food around in the oral | | | cavity until it is ready to be | | | swallowed | | | | | | -Important for eating and | | | speaking, and grooming | | | (especially in some animals) | +-----------------------------------+-----------------------------------+ | **Teeth (Incisors, Canines, | -Mechanical | | Premolars, Molars)** | digestion: breakdown food into | | | smaller pieces (chewing), making | | | chemical digestion more efficient | | | (increases the surface area for | | | enzymes in chemical digestion) | | | | | | **Types of Teeth**: | | | | | | -**Canines**: pointed and are | | | more prominent in some animals as | | | **fangs**; for puncturing and | | | shredding food | | | | | | -**Incisors**: flat, thin teeth | | | at the front, used for cutting | | | and biting off a piece of food | | | | | | -**Premolars and** **Molars**: | | | have cusps and ridges designed | | | for grinding and crushing food | | | | | | **[Adult Teeth,]** | | | each quadrant contains: | | | | | | -2 incisors | | | | | | -1 canine | | | | | | -2 premolars | | | | | | -3 molars (including the third | | | molar, or wisdom tooth) | | | | | | Total for a full set of **32 | | | adult teeth** | | | | | | **[Children's Teeth] | | | (up to age 5),** each quadrant | | | contains: | | | | | | 2 incisors | | | | | | 1 canine | | | | | | 2 molars (no premolars) | | | | | | Total for a full set of deciduous | | | teeth is **20 teeth** (5 in each | | | quadrant) | | | | | | **-Deciduous (Baby) Teeth**: | | | Primary teeth that fall out and | | | are replaced (*deciduous teeth = | | | teeth that \"fall out,\" like | | | leaves in autumn*); **deciduous | | | molars are replaced by adult | | | premolars.** | | | | | | **-Permanent Molars**: Erupt | | | without deciduous precursors (do | | | not get replaced). | +-----------------------------------+-----------------------------------+ | **Mastication** | To chew | +-----------------------------------+-----------------------------------+ | **Salivary Glands** | -Glands that produce saliva to | | | moisten and lubricate food, | | | aiding in easy swallowing | | | | | | -Saliva contains enzymes like | | | amylase, which start breaking | | | down starches, though food often | | | isn't chewed long enough for | | | significant digestion in the | | | mouth | +-----------------------------------+-----------------------------------+ **6. Pharynx: Structure and Function** +-----------------------+-----------------------+-----------------------+ | **Section of | **Location** | **Function** | | Pharynx** | | | +=======================+=======================+=======================+ | **Nasopharynx** | Behind the nasal | Passage for air; | | | cavity | prevents food from | | | | entering nasal | | | | cavity. | +-----------------------+-----------------------+-----------------------+ | **Oropharynx** | Behind the oral | Allows passage of | | | cavity | both food and air; | | | | aids in swallowing. | +-----------------------+-----------------------+-----------------------+ | **Laryngopharynx** | Above the esophagus | Point where the | | | and larynx | digestive and | | | | respiratory pathways | | | | split up; food to the | | | | esophagus and air to | | | | the larynx. | | | | | | | | **[Epiglottis]{.under | | | | line}** | | | | | | | | -Cartilage covered | | | | with soft tissue, | | | | located at the larynx | | | | entrance | | | | | | | | -Acts as **a | | | | protective flap**, | | | | closing over the | | | | larynx (airway) | | | | during swallowing to | | | | prevent food and | | | | liquids from entering | | | | the respiratory | | | | tract, ensuring food | | | | and liquids go down | | | | the esophagus | +-----------------------+-----------------------+-----------------------+ **7. Wall of the Digestive Tract (Aspects of the Digestive Tube)** +-----------------------------------+-----------------------------------+ | **Layer/Process** | **Description** | +===================================+===================================+ | **Lumen** | Open space or cavity of the | | | digestive tube | +-----------------------------------+-----------------------------------+ | **Mucosa (mucous membrane)** | **Innermost layer** with | | | epithelial cells, loose | | | connective tissue (lamina | | | propria), and a thin layer of | | | smooth muscle. | +-----------------------------------+-----------------------------------+ | **Submucosa** | Mainly loose connective tissue | | | layer containing blood vessels, | | | nerves, and lymphatic vessels. | +-----------------------------------+-----------------------------------+ | **Muscularis externa** | **Two smooth muscle layers:** | | | | | | 1.**Outer longitudinal layer:** | | | fibres run **lengthwise** along | | | the tube, helps in shortening the | | | tube and moving food along | | | | | | 2\. **Inner circular layer:** | | | fibres **going around the | | | tube;** helps in narrowing the | | | lumen and mixing the contents | | | by contracting and relaxing | | | | | | **The two muscle layers work | | | together to allow two | | | movements:** | | | | | | 1.**Peristalsis**: Wave-like | | | contractions propelling food | | | through the digestive tract | | | | | | 2\. **Segmentation**: muscular | | | action, particularly in the | | | intestines, used to mix | | | contents together back and | | | forth, enhancing digestion and | | | nutrient absorption by | | | thoroughly blending food with | | | digestive enzymes and | | | increasing contact with the | | | intestinal wall | +-----------------------------------+-----------------------------------+ | **Serosa** | -The **visceral peritoneum** | | | covering the digestive tract | | | (outermost layer) | +-----------------------------------+-----------------------------------+ | **Peristalsis** | Wave-like contractions propelling | | | food through the digestive tract. | +-----------------------------------+-----------------------------------+  **8. Esophagus: Location, Structure, and Function** +-----------------------------------+-----------------------------------+ | **Feature** | **Description** | +===================================+===================================+ | **Location & Length** | \- One of the structures found in | | | the mediastinum (posterior part) | | | | | | -A muscular tube about 25-30 cm | | | long, running from the pharynx | | | through the diaphragm to the | | | stomach | +-----------------------------------+-----------------------------------+ | **Structural Characteristics** | -Generally a smooth-walled tube, | | | but it does have folds in its | | | mucosa to allow it to expand when | | | food passes through and help it | | | return to its original shape when | | | empty | | | | | | -Has a mucous lining that helps | | | protect it from friction as food | | | passes through, but it lacks the | | | protective mucous barrier and | | | complexity of the stomach lining, | | | which is adapted to handle acidic | | | gastric secretions | | | | | | "**Pipe of Conduit":** carries | | | food/liquids from one place to | | | another | +-----------------------------------+-----------------------------------+ | **Epiglottis** | -Cartilage covered with soft | | | tissue, located at the larynx | | | entrance | | | | | | -Acts as a protective flap, | | | closing over the larynx (airway) | | | during swallowing to prevent food | | | and liquids from entering the | | | respiratory tract, ensuring food | | | and liquids go down the esophagus | +-----------------------------------+-----------------------------------+ | **Esophageal Hiatus** | An **opening through the | | | diaphragm** through which the | | | esophagus passes. | +-----------------------------------+-----------------------------------+ | **Cardioesophageal (or lower | -Nothing to do with the heart, | | esophageal) Sphincter** | but it's close to the heart (near | | | the heart region in the chest) | | (Sphincters: muscles that can | | | contract and pinch off) | -**Located where the esophagus | | | meets the stomach** and is | | | crucial for preventing acid from | | | moving up into the esophagus. | | | | | | -**T[ypically closed, | | | ]**but opens | | | temporarily for swallowing, | | | belching, or vomiting, allowing | | | food, liquids, or gas to pass | | | through as needed: This is | | | important because it prevents | | | acidic stomach contents from | | | flowing back into the esophagus, | | | which lacks the protective lining | | | to handle stomach acid. When the | | | sphincter doesn't function | | | properly, acid reflux occurs, | | | leading to the symptoms of | | | heartburn | +-----------------------------------+-----------------------------------+  **9. Stomach Anatomy and Function** +-----------------------------------+-----------------------------------+ | **Part** | **Description** | +===================================+===================================+ | **Fundus** | Upper, rounded part of the | | | stomach located just below the | | | diaphragm | +-----------------------------------+-----------------------------------+ | **Body** | Main central region where most of | | | the food mixing and digestion | | | occurs. | +-----------------------------------+-----------------------------------+ | **Pylorus** | Lower part of the stomach that | | | connects to the small intestine | | | (specifically the duodenum) | +-----------------------------------+-----------------------------------+ | **Pyloric Sphincter** | Muscular ring located at the | | | junction between the stomach and | | | the duodenum, the first part of | | | the small intestine (at the end | | | of the pylorus) | +-----------------------------------+-----------------------------------+ | **Greater & Lesser Curvatures** | **Greater curvature**: outer | | | curve of the stomach (left side) | | | | | | **Lesser curvature**: shorter, | | | inner curve on the right side of | | | the stomach, facing the liver | +-----------------------------------+-----------------------------------+ | **Muscle Layers** | **[-Three layers]**: | | | outer **longitudinal**, middle | | | **circular,** and inner | | | **oblique** (fibres are angled) | | | | | | -Muscle layer works together to | | | produce peristaltic movements, | | | mixing contents (chyme) | | | thoroughly, and gradually push it | | | toward the **pyloric sphincter** | +-----------------------------------+-----------------------------------+ | **Mucosa** | \- Parietal cells in the stomach | | | mucosa secrete hydrochloric acid | | | (HCl), which significantly lowers | | | the pH, creating a highly acidic | | | environment | | | | | | \- **The acidic environment is | | | necessary for the activation of** | | | pepsinogen into pepsin, an | | | **enzyme that begins the | | | breakdown of proteins in the | | | stomach**. Protein digestion | | | starts here and continues in the | | | small intestine. | | | | | | - The | | | stomach's mucosal cells produce a | | | **thick mucus layer** that **acts | | | as a protective barrier**, | | | shielding the stomach lining from | | | the harsh acidic environment and | | | digestive enzymes like pepsin, | | | which could otherwise damage the | | | stomach wall. | +-----------------------------------+-----------------------------------+ | **Rugae** | -Pleat-like folds in the | | | stomach's inner lining, allowing | | | it to stretch and expand to | | | accommodate a large volume of | | | food without damaging the tissue. | +-----------------------------------+-----------------------------------+ | **Peristalsis** | Wave-like muscle contractions | | | moving food along the digestive | | | tract. | +-----------------------------------+-----------------------------------+ | **Chyme** | Semiliquid mixture of partially | | | digested food and digestive | | | juices formed in the stomach. | +-----------------------------------+-----------------------------------+ | **Gastric Glands** | Glands in the stomach mucosa that | | | secrete hydrochloric acid, | | | digestive enzymes, mucus, and | | | hormones to aid in digestion and | | | protect the stomach lining | +-----------------------------------+-----------------------------------+ **10. Small Intestine Location, Structure and Function** +-----------------------------------+-----------------------------------+ | **Part** | **Description** | +===================================+===================================+ | **Duodenum** | -First part of the small | | | intestine | +-----------------------------------+-----------------------------------+ | **Jejunum** | -Middle section of the small | | | intestine | +-----------------------------------+-----------------------------------+ | **Ileum** | -Last section of the small | | | intestine | +-----------------------------------+-----------------------------------+ | **Plicae Circularis** | -Pleat-like, circular folds in | | | the lining of the small intestine | | | that increase the surface area, | | | enhancing nutrient absorption. | | | They also slow the movement of | | | food, giving enzymes more time to | | | break down nutrients effectively | | | | | | -**Most of the digestion and | | | absorption occurs in the small | | | intestine** | +-----------------------------------+-----------------------------------+ | **Intestinal Villi & Microvilli** | -**Villi:** small, finger-like | | | projections on the mucosal lining | | | of the small intestine. They | | | significantly increase the | | | surface area, allowing for more | | | efficient absorption of nutrients | | | | | | -**Microvilli:** small extensions | | | on the cell membranes of the | | | villi, forming what is called the | | | \"brush border.\" This structure | | | further increases surface area | | | and is the primary site where | | | nutrient absorption occurs | +-----------------------------------+-----------------------------------+ | **Intestinal Glands** | -The intestinal glands produce | | | digestive enzymes and mucus to | | | support absorption and digestion | | | | | | -The **chyme entering from the | | | stomach is highly acidic**. | | | **Small intestine enzymes require | | | a more neutral to slightly | | | alkaline environment. The | | | pancreas releases bicarbonate to | | | neutralize stomach acid, creating | | | an environment suitable for small | | | intestine enzymes to work | | | effectively.** | +-----------------------------------+-----------------------------------+ | **Blood Supply** | -Supplied by the superior | | | mesenteric artery (SMA), which | | | branches into vessels that supply | | | the duodenum, jejunum, and ileum | | | | | | -Venous blood from the small | | | intestine drains into the | | | superior mesenteric vein (SMV), | | | which then joins the portal vein | | | to carry nutrients to the liver | +-----------------------------------+-----------------------------------+ | **Lacteals** | -Specialized capillaries of the | | | lymphatic system in each villus | | | that absorb dietary fats. The | | | fats are transported through the | | | lymphatic system and eventually | | | enter the bloodstream at the | | | thoracic duct | +-----------------------------------+-----------------------------------+ | **Ileocecal Valve** | -Sphincter between the ileum | | | (last part of the small | | | intestine) and the cecum (first | | | part of the large intestine) | | | | | | \- Its main function is to | | | control the flow of digested | | | material from the small intestine | | | into the large intestine, | | | preventing backflow and ensuring | | | that contents move in the correct | | | direction through the digestive | | | tract | +-----------------------------------+-----------------------------------+  **11. Liver and Gallbladder Location, Structure and Function** +-----------------------------------+-----------------------------------+ | **Part** | **Description** | +===================================+===================================+ | **Hepatic Duct** | -Duct carrying bile from the | | | liver | | | | | | -**Common hepatic duct**= right + | | | left hepatic duct | +-----------------------------------+-----------------------------------+ | **Cystic Duct** | -Connects the gallbladder to the | | | **common bile duct**, | | | transporting stored bile. | +-----------------------------------+-----------------------------------+ | **Common Bile Duct** | -**Formed by the union of the | | | common hepatic duct** (from the | | | liver) **and the cystic duct** | | | (from the gallbladder) | | | | | | -The common bile duct carries | | | bile to the small intestine | | | (specifically the duodenum) to | | | aid in digestion and absorption | | | of fats. | | | | | | -**Sphincter of Oddi**: surrounds | | | the ends of the common bile duct | | | and pancreatic duct, controlling | | | the flow of bile and pancreatic | | | enzymes into the duodenum in | | | response to the presence of food | | | (chyme). | | | | | | -The arrival of chyme in the | | | small intestine triggers the | | | release of a hormone | | | (cholecystokinin, or CCK), which | | | signals the gallbladder to | | | contract and release bile | | | | | | -**Bile salts** (a component of | | | bile) **are released into the | | | small intestine to emulsify fats | | | as soon as chyme enters**, | | | helping break down lipids for | | | easier digestion and absorption | +-----------------------------------+-----------------------------------+ | **Bile and Bile Production** | -A greenish-yellow fluid | | | **produced by the liver** and | | | **stored and concentrated** | | | (removing some of the water and | | | electrolytes) **in the | | | gallbladder.** It is released | | | into the small intestine, where | | | it **emulsifies fats** for easier | | | digestion and also helps excrete | | | waste | | | | | | \- Bile production **involves | | | bile salts and waste products** | | | like bilirubin (a byproduct of | | | red blood cell breakdown) and | | | cholesterol | +-----------------------------------+-----------------------------------+  +-----------------------------------+-----------------------------------+ | **Emulsification and issue with | -Chyme (partially digested food) | | not having a gallbladder** | entering the small intestine has | | | a high water content, and because | | | lipids don't mix well with water, | | | they need bile salts to emulsify | | | them for effective enzyme action. | | | | | | -**Emulsification**: necessary to | | | keep lipids from clumping | | | together in the watery chyme, | | | allowing enzymes to digest them | | | effectively | | | | | | -Fat-soluble vitamins (like A, D, | | | E, and K) rely on fats for | | | absorption, so without proper | | | emulsification, absorption may be | | | reduced, leading to potential | | | deficiencies over time. | | | | | | **[Without a gallbladder: | | | ]** | | | | | | -Without a gallbladder, the body | | | lacks a storage for concentrated | | | bile, which can impact fat | | | digestion and absorption of | | | fat-soluble vitamins (A, D, E, | | | and K). | | | | | | -People without a gallbladder are | | | advised to eat smaller, frequent | | | meals to aid digestion, as bile | | | is continuously released in | | | smaller, less concentrated | | | amounts. | +-----------------------------------+-----------------------------------+ **12. Pancreas Location, Structure and Function** +-----------------------------------+-----------------------------------+ | **Part** | **Description** | +===================================+===================================+ | **Exocrine Portion and Endocrine | -Pancreas: a dual-function gland | | Portion** | with exocrine and endocrine | | | portions | | | | | | **[Exocrine portion: | | | ]** | | | | | | -Produces digestive enzymes that | | | are **released into the small | | | intestine (duodenum) via the | | | pancreatic duct** to aid in | | | digestion. | | | | | | **[Endocrine | | | portion:]** | | | | | | -**Ductless**, consisting of | | | **Islets of Langerhans** (like | | | little islands), which secrete | | | hormones (insulin and glucagon) | | | directly into the bloodstream to | | | regulate blood sugar. | | | | | | **-Ductless gland =** releases | | | hormones **directly** into the | | | bloodstream | +-----------------------------------+-----------------------------------+ | **Pancreatic Duct and | -Usually more than one duct (the | | Relationship to Common Bile | main duct and then the accessory | | Duct** | duct) | | | | | | -The main pancreatic duct usually | | | merges with the **common bile | | | duct**, allowing pancreatic | | | enzymes and bile to enter the | | | duodenum | +-----------------------------------+-----------------------------------+ | **Secretions (Exocrine)** | -Digestive enzymes released into | | | the **duodenum** via the | | | **pancreatic duct** | | | | | | -Includes enzymes like trypsin, | | | chymotrypsin, amylase, and lipase | | | that aid in digestion. | | | | | | **-***Trypsin and Chymotrypsin: | | | Break down proteins.* | | | | | | ***-**Amylase: Breaks down | | | carbohydrates.* | | | | | | ***-**Lipase: Breaks down fats* | +-----------------------------------+-----------------------------------+ | **Hormones (Endocrine)** | -Hormones released ) **directly | | | into the bloodstream** to | | | regulate blood sugar: | | | | | | -**insulin** (lowers blood | | | glucose) | | | | | | **-glucagon** (raises blood | | | glucose) | +-----------------------------------+-----------------------------------+  **13. Large Intestine Anatomy and Function** +-----------------------------------+-----------------------------------+ | **Structure** | **Description** | +===================================+===================================+ | **Ileo-cecal Valve** | -Sphincter located at the | | | junction of the **ileum** (the | | | last part of the small intestine) | | | and the **cecum** (the first part | | | of the large intestine) | +-----------------------------------+-----------------------------------+ | **Cecum** | -Blind-ended pouch, meaning it | | | doesn't continue directly but | | | serves as an entry point to the | | | large intestine | | | | | | -**First segment** of the large | | | intestine located in the lower | | | right abdominal quadrant. | | | | | | -Appendix hangs off it (lymphatic | | | organ) | +-----------------------------------+-----------------------------------+ | **Appendix** | -A small, tube-like lymphatic | | | organ, hanging off the cecum; | | | populated with lymphocytes and | | | contributes to immune functions. | +-----------------------------------+-----------------------------------+ | **Colon** | **-**The colon moves waste | | | material along, absorbing water | | | and electrolytes to form solid | | | stool for elimination | | | | | | **[Composed of four | | | parts]** (in order) | | | | | | **-Ascending colon** | | | | | | **-Transverse colon** | | | | | | **-Descending colon** | | | | | | **-Sigmoid colon** | +-----------------------------------+-----------------------------------+ | **Rectum** | -Final section of the large | | | intestine, storing feces before | | | defecation. | +-----------------------------------+-----------------------------------+ | **Anus** | -Terminal opening for feces | | | elimination, controlled by anal | | | sphincters. | +-----------------------------------+-----------------------------------+ | **Anal Sphincters** | -Internal (involuntary, smooth | | | muscle) and external (voluntary, | | | skeletal muscle) sphincters, both | | | working together to regulate | | | defecation | +-----------------------------------+-----------------------------------+ | **Teniae Coli** | -Three longitudinal muscle bands | | | on the large intestine that | | | create tension, forming the | | | intestine into pouch-like | | | segments called haustra | +-----------------------------------+-----------------------------------+ | **Haustra** | -Pouch-like segments created by | | | teniae coli contractions; These | | | haustra help move fecal matter | | | slowly through the colon, | | | allowing time for water and | | | electrolyte absorption | +-----------------------------------+-----------------------------------+ | **Blood Supply** | Primarily from the superior and | | | inferior mesenteric arteries, | | | providing nutrients to the large | | | intestine. | | | | | | -The **superior mesenteric artery | | | (SMA)** for the cecum, ascending | | | colon, and proximal transverse | | | colon. | | | | | | -The **inferior mesenteric artery | | | (IMA)** for the distal transverse | | | colon, descending colon, sigmoid | | | colon, and rectum | +-----------------------------------+-----------------------------------+ **14. Peritoneum Anatomy and Function** +-----------------------------------+-----------------------------------+ | **Characteristic** | **Description** | +===================================+===================================+ | **Location** | -**Lines the abdominal cavity** | | | | | | **-Consists of two layers**: | | | **parietal peritoneum** (lining | | | cavity wall) and **visceral | | | peritoneum** (covers the | | | abdominal organs). | +-----------------------------------+-----------------------------------+ | **Structure and Function** | A **serous membrane** that forms | | | a closed sac, with parietal and | | | visceral layers that encloses | | | most abdominal organs, providing | | | a lubricated environment that | | | reduces friction and supports | | | organ movement within the | | | abdominal cavity, and provides | | | passage for blood vessels, | | | nerves, and lymphatics (lymphatic | | | vessels) | +-----------------------------------+-----------------------------------+ **15. Mesentery and Greater Omentum Anatomy and Function** +-----------------------------------+-----------------------------------+ | **Structure** | **Description** | +===================================+===================================+ | **Mesentery** | -**Double layer of visceral | | | peritoneum** that connects the | | | intestines to the posterior | | | abdominal wall, providing support | | | and stability. | | | | | | -Also serves as a pathway for | | | **blood vessels, nerves, and | | | lymphatics** to reach the | | | intestines, facilitating nutrient | | | and waste transport | +-----------------------------------+-----------------------------------+ | **Greater Omentum** | -Large, fatty apron-like | | | peritoneal fold that hangs from | | | the stomach and drapes over the | | | intestines. | | | | | | -Plays roles in **insulating | | | abdominal organs**, **storing | | | fat**, and **isolating | | | infections** by limiting the | | | spread of inflammation within the | | | abdominal cavity | +-----------------------------------+-----------------------------------+  **[ADDITIONAL NOTES:]** **Order of Small Intestine: Duodenum → Jejunum → Ileum** **Section** **Location** **Structure** -------------- -------------------------------------------- --------------------------------------------------- **Duodenum** Upper abdomen, connects to stomach Short, C-shaped segment, about 25 cm long **Jejunum** Central abdomen Coiled, middle section with a thicker wall **Ileum** Lower abdomen, connects to large intestine Longest section with thinner walls, ends at cecum **Order of Large Intestine:** **Cecum → Ascending Colon → Transverse Colon → Descending Colon → Sigmoid Colon → Rectum → Anus** **Section** **Location** **Structure** ---------------------- --------------------------------------------- ---------------------------------------------------------- **Cecum** Lower right abdomen Pouch-like structure at the start of the large intestine **Ascending Colon** Right side of the abdomen Vertical tube running upward **Transverse Colon** Across the upper abdomen from right to left Horizontal tube **Descending Colon** Left side of the abdomen Vertical tube running downward **Sigmoid Colon** Lower left abdomen, S-shaped Curved, S-shaped structure **Rectum** Pelvis, at the end of the colon Muscular tube **Anus** Terminal end of the digestive tract Opening with sphincter muscles