3: Macronutrient Digestion
- Page ID
- 40942
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)You probably do not think too much about what actually happens to the food you eat. This section will describe in depth how what you eat is digested. The desired end result for the learner will be an integrated understanding of the process. This will require higher levels of thinking, but will prove to be well worth it in the end.
- 3.1: Digestion at a Glance
- This page outlines the digestion process, which breaks down food for absorption or excretion through the gastrointestinal (GI) tract consisting of organs like the mouth, stomach, and intestines. Accessory organs, including the salivary glands and liver, aid digestion without direct contact with food. Different enzymes, such as salivary amylase and pepsin, function in various GI locations to aid in this process.
- 3.2: Mouth to the Stomach
- This page explains that digestion begins in the mouth through mechanical (mastication) and chemical (enzymes like salivary amylase and lingual lipase) processes. Food forms a bolus and moves to the esophagus via the pharynx, assisted by the epiglottis. Peristalsis carries the bolus through the esophagus, but problems with the lower esophageal sphincter can result in acid reflux and heartburn, potentially indicating gastroesophageal reflux disease (GERD).
- 3.3: Stomach
- This page describes the process of digestion in the stomach, detailing how food passes through the lower esophageal sphincter and undergoes both chemical and mechanical digestion. It highlights the stomach's mucosa and its four cell types: G cells, chief cells, parietal cells, and neck cells, each with specific roles, including secreting gastrin, pepsinogen, hydrochloric acid, and mucus. The page concludes with chyme exiting the stomach into the small intestine through the pyloric sphincter.
- 3.4: Small Intestine
- This page discusses the structure and function of the small intestine, detailing its three sections (duodenum, jejunum, ileum) and its role in digestion. It highlights the importance of accessory organs (pancreas, liver, gallbladder) and the hormonal regulation of digestion.
- 3.5: Macronutrient Digestion Review
- This page offers a summary of the digestion processes for macronutrients including carbohydrates, proteins, triglycerides, cholesterol esters, and phospholipids, explaining how they are broken down for absorption into enterocytes. It also includes references for further reading on digestion.
- 3.6: Large Intestine
- This page explores the journey of undigested compounds like fiber in the large intestine, detailing its structure and functions, including the absorption of water and electrolytes, and feces formation. It emphasizes the importance of microbiota and the benefits of probiotics and prebiotics for gut health. Additionally, definitions of synbiotics and postbiotics are provided, and the text concludes by addressing recent scrutiny regarding health claims from probiotic product companies.