Anatomy Test 2

Digestive function

Mechanical and chemical breakdown of food

Mechanical digestion

Breakdown without enzymes like biting, chewing, crunching, grinding, etc to increase surface area

Chemical digestion

Requires enzymes for breakdown

Absorption

Transport of digested nutrients into ISF or bloodstream

Digestive anatomy

Alimentary canal and accessory organs

Alimentary canal

Gastrointestinal tract

Food tube

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus

8 meters long

Accessory organs

Create, store, and release digestive enzymes

Salivary glands, liver, gallbladder, pancreas

Wall structure of alimentary canal

4 layers

Mucosa, submucosa, muscular layer, and serosa

Mucosa

Inner mucous epithelium

Protects, secretes, and absorbs

Has villi, lamina propria, and muscularis mucosa

Lamina propria

Loose connective tissue in mucosa

Contains MALTS

Muscularis mucosa

Muscle in mucosa that helps provides folds that allows for stretching/distension

Submucosa

Connective tissue with numerous blood vessels, nerves, lymph vessels

Carries away materials

Has submucosa neural plexus

Muscularis externa

Two layers of smooth muscle

Inner circular layer

Outer longitudinal layer

Myenteric plexus between 2 layers

Submucosa neural plexus

Sensory neurons and ganglionic nerve fibers (ANS)

Myenteric plexus

Between circular and longitudinal layers

Sensory neurons and ganglionic nerve fibers

Enteric nervous system

Submucosa neural plexus and myenteric plexus combined

100M neurons (more than spinal cord)

Nervous system of digestive system

Serosa

Secretes serous fluid to reduce friction

Visceral peritoneum

Called adventitia in thoracic cavity and is more CT

Mesentery

Peritoneal membrane not attached to organ

Stabilize organ position

Has fat for padding

Access route for blood/lymph vessels and nerves (often to liver)

Alimentary canal motor functions

Segmentation and peristalsis

Segmentation

Nonrhythmic contractions

Mix with juices

Bring food in contact with mucosa for absorption

Mechanical digestion

Pacemaker cells set the frequency

Peristalsis

Ring of contraction then push bolus

Propelling

Circular muscles contract and longitudinal muscles shorten

GI control

Local factors stimulate stretch receptors (food) and chemoreceptors (pH)

Triggers myenteric plexus or triggers the CNS, specifically the brainstem

Hormones are released to stimulate secretion and digestion elsewhere

Ex: ileocecal reflex such as stomach being full causes some hormones to to affect the stomach and trigger small intestine sphincter to open

Mouth for digestive system

Mastication, tongue, palate, teeth, and salivary glands

Mastication

Physically grinding and mixing food for mechanical digestion

Oral cavity

Stratified squamous epithelial tissue

Protects against abrasion

Tongue

Skeletal muscle

Covered with papillae

Lingual lipase begins fat digestion

Lingual tonsils

Palate

Hard palate is bone

Soft palate is smooth muscle and ends at uvula

Uvula covers nasal cavity while eating

Palatine tonsils

Teeth

Not bone, made of enamel and dentin

Increases food surface area by mastication

Primary set has 20

Secondary set has 32

Incisors, cuspids, premolars/molars

Incisors

Front teeth for cutting large pieces

Cuspids

Puncture and shred food

Premolars/molars

For grinding food

Crown of tooth

Covered by glossy enamel which is crystalline Ca3(PO4)2

Cannot be replaced

Hardest structure in body

Internal living tissue is dentin

Pulp cavity of CT is lined with cells

Neck of tooth

Has sulcus where food may get stuck and bacteria grow and destroy enamel

Causes dental caries

Root of tooth

Dentin covered by cementum

Anchored by periodontal ligament

Salivary glands

Parotid, submandibular, and sublingual glands secrete saliva

Saliva

Solvent to dissolve food for taste and clean the mouth and teeth

Chemical digestion of starch and glycogen

Bicarbonate buffer to protect enzymes and teeth from acids

Contains lysozyme and IgA

Mucous cells produce a thick substance that forms a bolus with food

Serous cells produce watery substances and salivary amylase that breaks starch into disaccharides

Pharynx for digestive system

Shared passageway for food, water, and air

Function in deglutition (swallowing)

Nasopharynx, oropharynx, and laryngopharynx

Skeletal muscle

Nasopharynx

Connects nasal cavity to back of mouth

Filters out large particles (some by pharyngeal tonsils)

Oropharynx

Back of mouth

Laryngopharynx

Below mouth to esophagus

Epiglottis is trap door that closes off lungs

Remains contracted most of the time

Upper esophageal sphincter connects to esophagus and remains closed until swallowing

3 stages in deglutition

Buccal phase, pharyngeal phase, and esophageal phase

Buccal phase of degultition

Bolus is pushed pack and partially closes off soft palata

Voluntary

Pharyngeal phase of degultition

Tactile receptors on soft palate and uvula are stimulated and is involuntary

Brain stem sends motor command

Further closes soft palate

Muscles contract to push bolus down

Larynx elevates to close epiglottis

Esophageal phase of degultition

Peristalic waves of smooth muscle

No digestion and no new enzymes

Esophagus

Function in deglutition (swallowing), not digestion

Straight, collapsible tube, remains closed until deglutition

Carries food to stomach

Mucosal epithelia is stratified squamous

Serosa is adventitia

Esophageal hiatus in diaphragm allows esophagus to lead to stomach

Lower esophageal sphincter closes opening to stomach to prevent regurgitation

Specific mesenteries

Lesser omentum on lesser curvature of stomach

Greater omentum on greater curvature of stomach covers intestines and pads

Mesentery proper on small intestine

Mesocolon on large intestine

Stomach parts

Cardiac region, fundic region, body, pyloric region, pyloric sphincter

Has rugae

Cardia of stomach

Entrance to stomach

Neck

Has mucus

Fundus of stomach

Space for gas and storage at top of stomach

Body of stomach

Main functioning part

Mixing

Pylorus of stomach

End of stomach

Pyloric sphincter

Connects to small intestine

Point of no return

Rugae

Folds that mix and grind food

Allows distension to hold 4 liters of food

Layers of stomach

Has additional oblique muscle layer in muscularis externa for strength and mixing

Cells and secretions of stomach

Gastric pits/glands produce gastric juices

Mucous cells

Parietal cells

Gastrin

Chief cells

Mucous cells of stomach

Simple columnar epithelium

Produce mucus

Thick and alkaline for protection

Parietal cells of stomach

Intrinsic factor for vitamin B12 absorption in small intestine

HCl from H2CO3 and Cl-

Gastrin of stomach

Hormone for acid production and motility

Chief cells of stomach

Pepsinogen in the presence of HCl becomes pepsin to break down protein (first protein breakdown)

Gastric lipase

Chyme

Bolus mixed with gastric juices

3 phases of secretion and motility control

Cephalic phase, gastric phase, and intestinal phase

Cephalic phase

Centrally

Before reaching stomach

Sight, taste, smell, or thought of food stimulates gastric secretions and motility

Gastric phase

Locally

Food enters stomach

Distension and pH change

Stimulates gastric secretions

Mixing waves for 3-4 hours

Intestinal phase

Hormonally

Chyme is released into the intestine at a steady pace

Arriving chyme stimulates hormones

Inhibits stomach secretions and contractions

Liver

Accessory organ

Largest internal organ

Highly vascular

Everything absorbed goes to liver

Porta hepatis is opening

Fatty

Liver functions

Chemical factory

Stores Fe, vitamin A, and vitamin D

Removes (damaged RBCs) and detoxifies (drugs)

Carbohydrate metabolism by storing glycogen

Lipid metabolism by producing lipoproteins like HDL and LDl, cholesterol, and bile

Protein metabolism by amination, transamination, deamination, and plasma protein production

Bile

Yellowish green liquid secreted by hepatic cells

Emulsifier which makes fat droplets smaller

Contains water, bile salts, bile pigments, cholesterol, electrolytes

Amination

Production of amino acids

Transamination

Exchanges piece with other molecules to make amino acids

Deamination

Breakdown of proteins or amino acids

Amine group to ammonium to urea

Gall bladder

Accessory organ

Temporary storage for bile

Concentrates bile by absorbing water

Contents may precipitate to form gallstones which can block ducts and cause pigments to enter blood

Without it, fats cannot be digested as easily

Hepatopancreatic sphincter

Controls entry of bile and pancreatic juice into duodenum

Opens at meal time

Bile backs up to cystic duct which leads to gallbladder

Pancreas

Accessory organ

Acini cells excrete pancreatic juices that are alkaline to allow enzymes to work

Enzymes are pancreatic amylase, pancreatic lipase, nuclease, trypsin, chymotrypsin, and carboxypeptidase

Pancreatic amylase

Breaks down amylase to disaccharides

Pancreatic lipase

Breaks down triglycerides to diglycerides to monoglycerides

Nuclease

From pancreas

Breaks down nucleic acids like DNA and RNA to nucleotides

Trypsin/chymotrypsin

From pancreas

Break down proteins to peptides

Carboxypeptidase

From pancreas

Breaks down peptides to amino acids

Small intestine

Digestion, absorption, and transport

18-20 ft long

Highly folded for surface area and distension

Many forlds and villi

Duodenum, jejunum, and ileum

Duodenum

Short and fixed

Produces mucus

Jejunum and ileum

Chemical digestion and absorption

Lymph nodules/MALTs especially in ileum

Gut flora help digestion and produce sulfur and gas

Held by mesentery proper

Villi

Projections that increase surface area for absorption

Mucous membrane of simple columnar epithelium

Brush border of microvilli for enzymes and absorption

Secretions are mucus from goblet cells and enterokinase from intestinal glands

Enzymes are peptidase, sucrase, maltase, lactase, and intestinal lipase

Intestinal glands

Enterokinase converts trypsinogen to trypsin

Where new cells form

Peptidase

From small intestine villi

Breaks down peptides into amino acids

Sucrase, maltase, and lactase

From small intestine villi

Break disaccharides into monosaccharides

Celiac's disease

Proteins in gluten damage microvilli and prevent absorption

Large intestine

Absorbs H2O, electrolytes, and vitamins

Secretes mucus

Parts are cecum, appendix, colon, rectum, and anus

Cecum

First part of large intestine

Ileocecal valce connect small intestine to cecum

Collection, storage, and compaction of undigested material

Appendix

Part of lymphatic system

At end of cecum

Colon

Ascending colon, transverse colon, descending colon, sigmoid colon

Folds called haustra due to tight mucularis externa

Rectum

Connects large intestine to anus

Temporary storage of undigested material

Anus

Opening controlled by two sets of sphincters

Internal anal sphincter muscle is involuntary and smooth muscle

External anal sphincter muscle is voluntary and skeletal muscle

Feces

Undigested material

Water, electrolytes, mucus and epithelial cells, bacteria

Nutrition

Getting an adequate source for energy and material

Obtained by eating a variety of food

Metabolism

How nutrients are used

The sum of all the chemical processes in the body

2 processes

Nutrients

Chemicals supplied from the environment required for survival

Essential nutrients

Cannot be synthesized in body, must be obtained in diet

Macronutrients, micronutrients, and water

Macronutrients

Carbs, proteins, and lipids

Needed in large amounts

Micronutrients

Minerals and vitamins

Needed in small amounts

Water as nutrient

Can be synthesized by the body, but not in sufficient quantities, therefore it is essential

No nutritional value so not a nutrient