ABSORPTION AND EXCRETION -POWER POINT PRESENTATION

ABSORPTION AND EXCRETION

1. ABSORPTION AND EXCRETION OVERVIEW OF THE DIGESTIVE SYSTEM The digestive system is a complex network of organs responsible for breaking down food into smaller, usable nutrients that the body can absorb and utilize for energy, growth, and repair. This process involves both mechanical and chemical breakdown, starting in the mouth and continuing through the gastrointestinal tract. The digestive system also eliminates undigested waste products.

2. OVERVIEW OF THE DIGESTIVE SYSTEM Key Components: Gastrointestinal (GI) Tract: A long, continuous tube that extends from the mouth to the anus, including the mouth, pharynx, Esophagus, stomach, small intestine, and large intestine. Accessory Organs: These organs assist in the digestion process, but are not part of the GI tract. They include the liver, pancreas, gallbladder, teeth, tongue, and salivary glands. Functions: The digestive system performs several key functions: Digestion: Breaking down food into smaller molecules. Absorption: Absorbing nutrients into the bloodstream. Elimination: Removing waste products from the body.

3. OVERVIEW OF THE DIGESTIVE SYSTEM How it Works: Ingestion: Food enters the mouth and is mechanically broken down by teeth and mixed with saliva. Chemical Digestion: Enzymes in saliva start breaking down carbohydrates. Movement: Food is swallowed and moves through the esophagus into the stomach. Stomach: The stomach further breaks down food mechanically and chemically, churning food and adding hydrochloric acid and digestive enzymes. Small Intestine: Most of the digestion and absorption of nutrients occurs in the small intestine, with the help of enzymes from the pancreas and bile from the liver. Large Intestine: Undigested food and water are absorbed in the large intestine, forming stool. Elimination: Stool is eliminated from the body through the anus.

4. OVERVIEW OF THE DIGESTIVE SYSTEM

5. HISTOLOGY The digestive system's histology, or tissue structure, is characterized by four main layers: mucosa, submucosa , muscularis propria , and serosa (or adventitia). The mucosa, the innermost layer, lines the digestive tract and varies in structure depending on the specific region. The submucosa , beneath the mucosa, is a connective tissue layer containing blood vessels and nerves. The muscularis propria , a muscular layer, facilitates movement through the digestive tract. Finally, the outermost layer, serosa or adventitia, connects the digestive tract to surrounding tissues

6. HISTOLOGY 1. Mucosa: Epithelium: The innermost layer, which varies depending on the region (e.g., stratified squamous in the esophagus , simple columnar in the stomach and intestines). Lamina Propria: A connective tissue layer supporting the epithelium, containing blood vessels, lymphatic tissue, and glands. Muscularis Mucosae: A thin layer of smooth muscle that can cause folds in the mucosa.

7. HISTOLOGY 2. Submucosa: A layer of loose connective tissue containing blood vessels, lymphatic vessels, and nerves (e.g., Brunner's glands in the duodenum and lymphoid aggregates in the ileum). 3. Muscularis Propria: Two layers of smooth muscle, an inner circular layer and an outer longitudinal layer, responsible for peristalsis. In the stomach, a third layer of smooth muscle (oblique) is present. 4. Serosa/Adventitia: Serosa: Covers organs that are freely mobile within the abdominal cavity (e.g., stomach, intestines). Adventitia: Covers organs that are retroperitoneal (e.g., esophagus , part of the colon)

8. HISTOLOGY

9. MOUTH AND PHARYNX The mouth and pharynx play crucial roles in the early stages of the digestive process. The mouth initiates mechanical and chemical digestion, while the pharynx acts as a passageway to the esophagus , facilitating swallowing Mouth (Oral Cavity): Mechanical Digestion: Teeth and tongue break down food into smaller pieces, increasing surface area for enzymatic action. Chemical Digestion: Saliva, produced by salivary glands, moistens food and contains enzymes like amylase that begin the breakdown of starches. Bolus Formation: The tongue mixes the food with saliva, forming a soft, compact mass called a bolus, ready for swallowing

10. MOUTH AND PHARYNX Pharynx: Passageway: The pharynx (throat) is a shared pathway for both air (respiratory system) and food (digestive system). Swallowing: During deglutition (swallowing), the soft palate rises to close off the nasopharynx , preventing food from entering the nasal cavity. Pharyngeal Phase: The tongue pushes the bolus back, triggering the involuntary pharyngeal phase of swallowing, where the larynx elevates, the epiglottis folds over the glottis to protect the airways, and the bolus is propelled into the esophagus . Esophagus: The pharynx connects to the esophagus , a muscular tube that carries the bolus to the stomach

11. MOUTH AND PHARYNX

12. ESOPHAGUS The esophagus is a muscular tube that acts as a passage for food and liquids from the pharynx (throat) to the stomach. It's about 10 inches long and 1 inch in diameter. The esophagus's primary function is to propel food and liquids to the stomach via rhythmic muscular contractions called peristalsis

13. ESOPHAGUS Key aspects of the esophagus : Structure: The esophagus is a muscular tube with four layers (mucosa, submucosa , muscularis , and adventitia). Location: It's located in the center of the chest, behind the trachea (windpipe) and in front of the spine

14. ESOPHAGUS Function: Transporting Food and Liquids: It moves chewed food (bolus) from the mouth to the stomach. Preventing Food from Entering the Windpipe: The esophagus helps to prevent food from entering the trachea. Preventing Stomach Contents from Backing Up: The upper and lower esophageal sphincters (ring-shaped muscles) help to prevent stomach contents from flowing back into the esophagus .

15. ESOPHAGUS Peristalsis: Rhythmic waves of muscular contractions that propel food through the esophagus . Sphincters: The upper and lower esophageal sphincters act like one-way valves, controlling the flow of food and preventing reflux. Anatomical Divisions: The esophagus is divided into three sections: cervical (top), thoracic (middle), and abdominal (bottom

16. ESOPHAGUS Symptoms of Esophageal Issues: Heartburn: Burning sensation in the chest due to stomach acid refluxing into the esophagus . Difficulty Swallowing (Dysphagia): A feeling like food gets stuck in the throat or chest. Chest Pain: Can be associated with various esophageal conditions. Regurgitation: The backward flow of stomach contents

17. STOMACH The stomach plays a crucial role in the digestive system by physically and chemically breaking down food. It receives food from the esophagus , mixes it with digestive juices containing acids and enzymes, and then churns it into a liquid called chyme . The pylorus, a muscular valve, regulates the release of chyme into the small intestine

18. STOMACH ingestion and Propulsion: The stomach receives food from the esophagus via the lower esophageal sphincter. Once in the stomach, the food is mixed with digestive juices. Mechanical Digestion: The stomach's strong muscular walls contract and mix the food, physically breaking it down into smaller pieces. Chemical Digestion: Digestive juices containing hydrochloric acid and enzymes (like pepsin) are secreted into the stomach to further break down food, particularly proteins.

19. STOMACH Storage: The stomach can temporarily store food, allowing for a more controlled and gradual release of chyme into the small intestine. Regulation of Chyme Release: The pyloric sphincter controls the rate at which chyme is released into the duodenum, the first part of the small intestine

20. SMALL INTESTINES The small intestine is a crucial part of the digestive system, responsible for absorbing most nutrients and fluids from food after it has been partially broken down in the stomach and further digested by the pancreas and liver. It connects the stomach to the large intestine and is about 20 feet long, with three sections: the duodenum, jejunum, and ileum

21. SMALL INTESTINES

22. SMALL INTESTINES Function: The small intestine continues the digestive process, breaking down food into smaller, absorbable units like vitamins, minerals, carbohydrates, fats, and proteins. Absorption: It absorbs these nutrients, as well as water, which can be used by the body. Location: The small intestine is a long, tube-like organ that stretches from the stomach to the large intestine, folding many times to fit inside the abdomen.

23. SMALL INTESTINES Sections: The three parts of the small intestine are the duodenum, jejunum, and ileum. Digestion: The small intestine also releases its own digestive juices, which help break down proteins, carbohydrates, and fats, working together with bile from the liver and pancreatic juice from the pancreas

24. LARGE INTESTINES The large intestine, also known as the colon, is the final part of the digestive system, responsible for absorbing water and electrolytes from undigested food. It transforms the remaining waste into stool and stores it before elimination. The large intestine includes the cecum, colon (ascending, transverse, descending, and sigmoid), rectum, and anus

25. LARGE INTESTINES

26. LARGE INTESTINES Key Functions of the Large Intestine: Water and Electrolyte Absorption: The large intestine absorbs water and electrolytes from the remaining waste, which helps to solidify the stool. Feces Formation: The absorbed water and electrolytes contribute to the formation of stool. Storage and Elimination: The rectum stores the stool, and the anus facilitates its expulsion from the body. Vitamin Production: Certain bacteria in the colon produce B vitamins (B12, thiamin , riboflavin) and vitamin K.

27. LARGE INTESTINES Anatomy of the Large Intestine: Cecum: The first part of the large intestine, receiving waste from the small intestine. Colon: The longest portion of the large intestine, divided into ascending, transverse, descending, and sigmoid sections. Rectum: The final section of the large intestine, storing stool before elimination. Anus: The opening through which stool is expelled.

28. LIVER The liver plays a crucial role in the digestive system by producing bile, which emulsifies fats and aids in their absorption. It also metabolizes nutrients, detoxifies harmful substances, and stores nutrients like vitamins and iron. 1. Bile Production: The liver produces bile, a fluid that is stored in the gallbladder. Bile is released into the small intestine to help break down and absorb fats. Without bile, the body would struggle to digest and absorb dietary fats

29. LIVER 2. Nutrient Metabolism: The liver processes and metabolizes nutrients absorbed from the digestive tract. It converts carbohydrates, proteins, and fats into forms the body can use. The liver also synthesizes and releases proteins needed for various bodily functions. 3. Detoxification: The liver plays a vital role in detoxifying the body from harmful substances. It filters blood coming from the digestive system, removing toxins and waste products. The liver can convert harmful substances into less toxic or harmless forms for excretion

30. LIVER 4. Nutrient Storage: The liver stores essential nutrients like vitamins, minerals, and glycogen (a form of stored carbohydrates). These stores are released into the bloodstream when the body needs them

31. PANCREAS The pancreas plays a crucial role in the digestive system by producing digestive enzymes and hormones. Specifically, it secretes pancreatic juices containing enzymes that break down fats, carbohydrates, and proteins in the small intestine. It also produces hormones like insulin and glucagon that regulate blood sugar levels

32. PANCREAS 1. Digestive Enzyme Production: The pancreas produces a variety of enzymes that are essential for breaking down food. These enzymes, including lipase, protease, and amylase, are secreted into the duodenum (the first part of the small intestine), where they help to break down fats, proteins, and carbohydrates. Pancreatic juices also contain bicarbonate, which helps neutralize the acidity of the stomach contents as they enter the small intestine.

33. PANCREAS 2. Hormone Production: The pancreas also acts as an endocrine gland, producing hormones that regulate blood sugar levels. Insulin, produced by the islets of Langerhans in the pancreas, helps the body absorb glucose (sugar) from the bloodstream into cells for energy. Glucagon, another hormone produced by the pancreas, stimulates the release of glucose from the liver into the bloodstream when blood sugar levels are low.

34. PANCREAS Draw the biliary tree

35. NUTRITION CARBOHYDRATES Carbohydrate digestion is a process where complex carbohydrates are broken down into simpler sugars (monosaccharides) like glucose, which the body can absorb and use for energy. This process begins in the mouth with saliva and continues in the small intestine with enzymes from the pancreas and intestinal lining

36. NUTRITION 1. Digestion Begins in the Mouth: Salivary amylase, an enzyme in saliva, starts the breakdown of starch (a complex carbohydrate) into shorter chains of glucose (dextrins and maltose). This initial breakdown occurs in the mouth during chewing. 2. Digestion Continues in the Small Intestine: The partially digested carbohydrates (dextrins and maltose) move from the mouth to the stomach, then into the small intestine. In the duodenum (the first part of the small intestine), pancreatic amylase and enzymes from the intestinal lining (brush border enzymes) further break down carbohydrates into simpler sugars (monosaccharides like glucose, fructose, and galactose). These monosaccharides are then absorbed into the bloodstream through the intestinal lining.

37. NUTRITION 3. Role of Insulin and Blood Sugar: As blood glucose levels rise after carbohydrate digestion, the pancreas releases insulin. Insulin signals cells throughout the body to absorb glucose from the bloodstream for energy or storage (as glycogen in the liver and muscles). When blood sugar levels drop, the pancreas releases glucagon, which signals the liver to release stored glucose back into the bloodstream to maintain stable blood sugar level.

38. NUTRITION 4. Fiber's Role: Fiber, a type of carbohydrate, is not digested by the body and therefore doesn't provide energy. However, fiber is important for digestive health, contributing to bowel movements, regulating blood sugar, and supporting gut microbiota. Fiber can also be fermented by bacteria in the large intestine, producing short-chain fatty acids that can be used as an energy source.

39. PROTEINS Proteins are digested in the stomach and small intestine with the help of enzymes. In the stomach, the enzyme pepsin breaks down proteins into smaller peptide chains. In the small intestine, pancreatic enzymes like trypsin and chymotrypsin further break down these peptides into smaller amino acids or tripeptides and dipeptides, which are then absorbed into the bloodstream.

40. PROTEINS 1. Stomach: When food containing protein enters the stomach, hydrochloric acid and the enzyme pepsin begin the process of breaking down the protein into smaller peptide chains. 2. Small Intestine: Pancreatic Enzymes: As the partially digested protein enters the small intestine, the pancreas releases enzymes like trypsin and chymotrypsin, which further break down the peptides into smaller amino acids, tripeptides, and dipeptides. Other Intestinal Enzymes: The small intestine lining also releases its own enzymes that help to break down the smaller peptides into individual amino acids. Absorption: These amino acids, tripeptides, and dipeptides are then absorbed into the bloodstream through the lining of the small intestine, specifically through the microvilli.

41. PROTEINS Enzymes Involved: Pepsin (Stomach): Breaks down proteins into smaller peptide chains. Trypsin and Chymotrypsin (Pancreas): Further break down peptides into smaller amino acids, tripeptides, and dipeptides. Other Intestinal Enzymes: Break down peptides into individual amino acids

42. LIPIDS Lipid digestion primarily occurs in the small intestine, facilitated by bile salts and pancreatic lipase. Bile salts emulsify fats, breaking them into smaller droplets, while pancreatic lipase breaks down triglycerides into free fatty acids and monoglycerides. The resulting fatty acids and monoglycerides are then absorbed into the intestinal cells and reassembled into triglycerides, which are then packaged into chylomicrons for transport into the lymphatic system.

43. LIPIDS 1. Stomach: Lipids enter the stomach, where they are not significantly digested. However, gastric lipase (a minor enzyme) can break down some triglycerides into fatty acids and monoglycerides. 2. Small Intestine: The primary site for lipid digestion. Emulsification: Bile, produced by the liver and stored in the gallbladder, is released into the duodenum (the first part of the small intestine). Bile salts, which are a component of bile, act as emulsifiers, breaking large fat globules into smaller droplets, increasing the surface area for enzymatic digestion.

44. LIPIDS Enzymatic Digestion: Pancreatic lipase, secreted by the pancreas, hydrolyzes triglycerides into free fatty acids and monoglycerides. Micelle Formation: Bile salts cluster around the products of digestion (fatty acids and monoglycerides) to form micelles, which help them dissolve in the watery environment of the small intestine. Micelles also facilitate absorption by bringing the digested fats close to the intestinal cells' microvilli.

45. LIPIDS 3. Absorption: Fatty acids and monoglycerides are absorbed into the epithelial cells lining the small intestine. 4. Reassembly and Transport: Inside the intestinal cells, the fatty acids and monoglycerides are reassembled into triglycerides. These triglycerides are then combined with other lipids and proteins to form chylomicrons. Chylomicrons are then released into the lymphatic system and eventually enter the bloodstream, where they transport lipids throughout the body.

46. VITAMINS AND MINERALS The digestive system is responsible for absorbing vitamins and minerals from food. Specific organs, like the duodenum, are key sites for nutrient absorption. Vitamins and minerals play vital roles in digestion and overall health, with some nutrients even influencing the absorption of others.

47. VITAMINS AND MINERALS Key Vitamins and Minerals for Digestive Health: Vitamin A: Nourishes the lining of the gastrointestinal tract, supporting immune function and overall health. B Vitamins: Aid in nutrient breakdown and energy production, ensuring efficient digestive processes. Vitamin C: Essential for collagen production, which is crucial for maintaining the integrity of the digestive tract tissues. Vitamin D: Helps the body absorb calcium, which is vital for bone health and is also used in digestion

48. VITAMINS AND MINERALS Calcium: Strengthens teeth, which are needed for chewing, and also plays a role in muscle function, including those of the digestive tract. Magnesium: Can help prevent constipation and promote regular bowel movements. Zinc: Enhances the sense of smell, which can improve appetite and digestion. Other Important Minerals: Copper, iron, potassium, and selenium also play crucial roles in digestion and overall health

49. VITAMINS AND MINERALS Absorption Process: Duodenum: The duodenum, the first part of the small intestine, is a primary site for the absorption of many vitamins and minerals. Villi: Intestinal villi, small finger-like projections, increase the surface area for nutrient absorption. Fat-soluble vitamins (A, D, E, K): Are absorbed with dietary fats. Water-soluble vitamins (B vitamins, C): Are absorbed directly into the bloodstream. Mineral Absorption: The absorption of minerals like iron and calcium can be regulated by the body's needs

50. VITAMINS AND MINERALS Factors Influencing Absorption: Dietary Intake: Adequate intake of vitamins and minerals is crucial for proper absorption. Other Nutrients: Some nutrients can enhance the absorption of others (e.g., vitamin C increases iron absorption). Underlying Health Conditions: Conditions like celiac disease or Crohn's disease can affect nutrient absorption