ch 7 - digestive system

3 main functions of DS

1. break down food consumed

2. releases nutrients

3. absorbs nutrients into body

2 most central partnerships of DS

• endocrine system

• cardiovascular system

name the components that:

• regulate and control digestion

• transport nutrients

• hormones

• blood and lymph

2 main parts of DS structure

alimentary canal - food actually passes through this tract

accessory structures - sits outside of the tract, may secrete fluids and enzymes

provide a list of organs found in both alimentary and accessory portions of the DS

alimentary:

• mouth

• pharynx

• esophagus

• stomach

• SI, LI

accessory:

• teeth, tongue

• liver

• gallbladder

• pancreas

alimentary canal (def + 4 tissue layers)

the gut - one-way passageway for food + derivatives

4 tissue layers

• mucosa

• submucosa

• muscularis

• serosa

accessory structures

organs/structures assisting in food processing

label the alimentary canal tissue layers and structures

describe 4 tissue layers of alimentary canal (provide names + structural details)

1. mucosa: produces mucous

   1. epithelium lining lumen

   2. lamina propria (connective tissue)

   3. muscularis mucosae (pulls mucosa into folds for digestion)

   4. goblet cells (secrete mucous)

   5. endocrine cells (produce hormones)

2. submucosa: connects mucosa to muscularis

   1. blood and lymph vessels

   2. submucosal plexus (nerve network for sensory input)

3. muscularis:

   1. 2-3 layers of smooth muscle in stomach

   2. 2 layers of smooth muscle in intestines

   3. skeletal muscle at mouth, pharynx, anal sphincter for swallowing/defecation

4. serosa: outermost layer, only in abdominal cavity

   1. visceral peritoneum (over loose areolar connective tissue)

   2. adventitia (collagen fiber layer holding structures in place)

peritoneum

serous membranes lining the digestive organs in abdominal cavity

• parietal peritoneum = lines abdominal wall

• visceral peritoneum = surrounds abdominal organs

label peritoneal structures

(6) list overview of digestion steps

1. ingestion

2. propulsion

3. mechanical digestion

4. chemical digestion

5. absorption

6. defecation

ingestion (def, steps)

entry of food into alimentary canal

1. food into mouth

2. saliva (contains enzymes to begin digestion)

3. chewing → becomes BOLUS to swallow

propulsion (def, steps)

movement of food through digestive tract

1. swallowing (tongue, pharyngeal muscles bring food into esophagus)

2. peristalsis (alternating contractions of longitudal and smooth muscle in alimentary canal wall)

mechanical digestion (def, methods involved)

process making food smaller for digestion, makes pieces easier to pass thru system

• mastication (chewing)

• tongue manipulation (mixing food w/ saliva)

• chyme creation (churning food in stomach)

• segmentation (SI circular muscle contraction)

chemical digestion (def, steps)

enzymes break down nutrients into chemical building blocks

• begins: mouth

• completed: SI

digestive secretions: speed up chemical reactions w/ enzymes

extracellular digestion in lumen of alimentary canal

absorption (def, processes involved)

uptake of nutrients entering blood + lymph

• epithelial cells lining lumen: absorb nutrients into bloodstream

• lacteals: lipids enter these to get to bloodstream

defecation (def)

remove unused/indigested materials as feces through the anus

name the receptors the alimentary canal contains for nervous control of digestion

• mechanoreceptors (touch)

• chemoreceptors (chemical stimuli)

• osmoreceptors (osmotic pressure)

label the red boxes of the mouth/oral cavity

teeth (funct, #)

• # deciduous

• # permanent

  • # incisors

  • # cuspids

  • # premolars

  • # molars

mechanically break down food

• 20 deciduous teeth (baby teeth)

• 32 permanent teeth

  • 8 incisors

  • 4 cuspids

  • 8 premolars

  • 12 molars

for the following structures, describe their desired movement and effect

1. lips and cheeks

2. salivary glands

3. tongue’s extrinsic muscles

4. tongue’s intrinsic muscles

5. taste buds

6. lingual glands

7. teeth

1. hold food btwn teeth; ensure food is chewed evenly

2. secrete saliva; moisten interior of mouth, food, soften food

3. move tongue sideways, in and out: shape food into bolus

4. change tongue shape: manipulate food to be swallowed

5. sense taste and food: nerve impulses stimulate glands, resulting in saliva secretion

6. secrete lingual lipase: in stomach, breaking down triglycerides

7. mechanical digestion: breaks food into smaller particles for digestion

describe the following structures of the mouth/oral cavity

• Labia

  • Labial frenulum, gums

• Cheeks

• Oral vestibule

  • Fauces

  • Palate

    • Hard palate

    • Soft palate

    • Uvula

  • Tongue

• labia: LIPS, regulating what goes in and out

  • labial frenulum: attaches each lip to gums

• cheeks: side walls of the mouth

• oral vestibule: inner chamber of the mouth

  • fauces: opening between mouth and oropharynx

  • palate: roof of mouth

    • hard palate: (anterior) separates nasal and oral cavity

    • soft palate: (posterior) skeletal muscle, not rigid

    • uvula: bead of tissue dropping from soft palate

  • tongue: skeletal muscle for ingestion, digestion, sensation, swallowing

name the structures that move upward when swallowing to prevent food from entering the nasal cavity

soft palate and uvula

papillae

bumps on the tongue containing taste buds and touch receptors

glands of mouth/oral cavity

• salivary glands: within mucous membranes

  • exocrine glands: secrete saliva into the mouth

    • submandibular glands

    • sublingual glands

    • parotid glands

saliva (chemical makeup + enzyme)

water (>95%), ions, enzymes, glycoproteins

• enzyme: salivary amylase - starch breakdown

submandibular glands (location)

(exocrine glands, secrete saliva into mouth)

floor of mouth

sublingual glands (location)

(exocrine glands, secrete saliva into mouth)

below the tongue

parotid glands (location)

(exocrine glands, secrete saliva into mouth)

between skin and masseter muscle near the ears

pharynx

muscular passageway connecting oral, nasal cavities to esophagus

• nasopharynx: breathing, speech

• oropharynx: breathing, digestion

• laryngopharynx: breathing, digestion

describe how the pharynx and esophagus are used during swallowing

pharynx raises and expands to receive bolus, which is forced into esophagus

esophagus

muscular passageway connecting pharynx to stomach

• route goes through mediastinum

• enters abdomen through esophageal hiatus

label the esophageal regions

deglutition (def, list stages)

swallowing - movement of food from mouth to stomach by tongue muscles, pharynx, esophagus, mucus + saliva

1. voluntary stage

2. pharyngeal phase

3. esophageal phase

expand on the stages of deglutition (describe movements with specific structural names)

1. voluntary stage: swallowing food

   1. tongue moves up and back

   2. bolus pushed into oropharynx

2. pharyngeal phase:

   1. soft palate + uvula close off nasopharynx

   2. nasopharynx is closed → deglutition apnea (breathing ceases) occurs

   3. pharyngeal constrictor muscles move bolus to upper esophageal sphincter

   4. bolus enters esophagus

3. esophageal phase:

   1. peristalsis moves bolus down to lower esophageal sphincter

   2. lower esophageal sphincter relaxes → bolus enters stomach