GI System

QU Anatomy

what set of organs break down food items into nutrients

organs of the alimentary canal

accessory organs

what is the alimentary canal

continuous tube through which food passes directly

GI / Digestive tract

what are the organs of the alimentary canal

oral cavity, pharynx, esophagus, stomach, small intestine, large intestine

what do the accessory organs do in digestion

assist as they do not directly touch food (except teeth and tongue)

what are the accessory organs in degestion

teeth, tongue, salivary glands, liver, gallbladder and pancreas

what are the three anatomical divisions of the pharynx

nasopharynx

oropharynx

laryngopharynx

where is the nasopharynx located

posterior to nasal cavity

what is the function of the nasopharynx

warming, humidifying and filtering inspired air

the nasopharynx extends from what structure to what structure

posterior nares to the uvula

what do the uvula and soft palate do during swallowing

both structures move posteriorly to prevent food from entering the nasopharynx and nasal cavity

what does the nasopharynx contain

abundant amounts of lymphoid tissue

where is the oropharynx located

posterior to oral cavity

the oropharynx spans from what structure to what structure

the uvula to the larynx (epiglottis)

what structures does the laryngopharynx span between

from hyoid bone to esophagus

what does the laryngopharynx open to anteriorly

opens into the larynx

what does the laryngopharynx open to inferiorly

opens into the esophagus

what are the functions of both the oropharynx and the laryngopharynx

protective against mechanical stress since their cavities are a passageway for both air and food

what type of epithelium lines the oropharynx and laryngopharynx

nonkeratinized stratified squamous epithelium

what type of epithelium lines the nasopharynx

pseudostratified ciliated columnar epithelium

in relation to the pharynx, where is the oral cavity located

anteriorly

what forms the anterior wall of the oral cavity

the lips

what muscle forms the lips

orbicularis oris muscle

what are behind the lips and housed in bony sockets

the teeth

what are the bony sockets teeth lie in covered by

gums / gingivae

what attaches the internal surface of the lips to gums on midline

labial frenulum

what is the narrow space between teeth and gums as well as the internal surfaces of lips and cheeks

the oral vestibule

what forms the lateral wall of the oral cavity

the cheeks

what muscle are the cheeks composed of

the buccinator muscles

what is the inferior wall of the oral cavity composed of

the muscles of the tongue and muscles that attach to the hyoid bone

what is the narrow band of mucosa that connects the tongue to the floor of the mouth

the lingual frenulum

what does the lingual frenulum do

prevents the tongue from moving too far posteriorly

what is the superior boundary of the oral cavity

the palate

what are the two portions that make up the palate

anterior 2/3 is the hard palate

posterior 1/3 is the soft palate

describe the hard palate

made up from the maxillary and palatine bones

slightly rough surface

assists in mechanical digestion

describe the soft palate

arch-shaped

projection called the uvula extends inferiorly

why do the soft palate and the uvula move posteriorly during swallowing

to prevent food from entering the nasal cavity

what is the posterior wall of the oral cavity formed by

the faucial arches just anterior to the tonsils

what type of muscle controls the movement of the tongue

skeletal muscle

• extrinsic muscles

• intrinsic muscles

what do the extrinsic muscles of the tongue do

control position of the tongue

• move during chewing and turn food into bolus

what do the intrinsic muscles of the tongue do

control shape and size of the tongue

• push food against the hard palate and push food posteriorly

how is the epithelium of the tongue arranged

arranged into small projections called papillae

• papillae = taste buds

• four types based on shape

describe filiform papillae

• long, thin, cylinders

• no taste buds

• detect food texture and temperature

• assist in mechanical digestion

• evenly distributed over anterior 2/3 of tongue

• covered with stratified squamous keratinized epithelium

  • make the surface of the tongue rough

• run parallel to the terminal sulcus

describe vallate (circumvallate) papillae

• largest of the 4 classes

• dome-shaped

• contain 100s of taste buds

• live directly anterior to terminal sulcus

• circular trenches surround the papillae

describe the fungiform papillae

• mushroom-shaped

• contain only a few taste buds

• scattered along tong —> sides and tip

describe foliate papillae

• ridges on sides of tongue

• only contain taste buds in childhood

what nerves provide special sensation for the tongue (taste buds)

CN VII, IX and X

what nerves provide general sensation to the tongue

VNV₃ , IX and X

• touch and temperature

what nerve provides motor activity to the tongue

CN XII

• all intrinsic muscles

• all extrinsic muscles expect palatoglossus

  • genioglossus, hyoglossus, styloglossus

where do the artery branches of the tongue arise from

lingual artery

what is the path of blood through the veins in the tongue

dorsal lingual, deep lingual, sublingual veins —> lingual vein —> internal jugular vein

why are nitroglycerin tablets given sublingually

• they are dissolved and absorbed by the lingual veins

• they bypass the digestive system

what is the treatment purpose for nitroglycerin

treat episodes of angina in people who have coronary artery disease

what two areas make up the dorsum / dorsal surface of the tongue

anterior surface (body)

posterior surface (root)

what is the terminal sulcus of the tongue

a dividing line that separates the dorsum into the anterior 2/3 and posterior 1/3

what are the two structures in the posterior dorsum

foramen cecum

• remnant of proximal part of the thyroglossal duct

lingual tonsil

describe the inferior surface of the tongue

rests on the floor of the mouth

what is the connective band found under the tongue’s inferior surface

lingual frenulum

what is the midline groove of the tongue

median sulcus

what is the epiglottic vallecula

the space between the back of the tongue and epiglottis

what is the throat

the space between the oral cavity and the pharynx

what makes up the anterior portion of the throat

palatoglossal arch and muscle

what makes up the posterior portion of the throat

palatopharyngeal arch and muscle

what is the isthmus of fauces (oropharyngeal isthmus)

palatine tonsil

what is another name for Waldeyer’s (tonsillar) ring

pharyngeal lymphatic ring

what is the tonsillar ring and what is it formed by

an incomplete circular band

formed by:

• palatine tonsils

• lingual tonsils

• pharyngeal tonsils (adenoid)

what do large tonsils cause

obstructed breathing

describe the features of the teeth

• located in bony sockets —> dental alveoli

• held in place by bands of connective tissue —> periodontal ligament

what are the two components of tooth anatomy

• crown

  • visible portion above gum line

  • hard outer layer = enamel

  • inner gelatinous layer = pulp

• root

  • embedded within dental alveolus

describe the 3 types of tooth shape

1. incisors

   1. broad and flat with a narrow crown

   2. for cutting off pieces of food

2. canines

   1. aka cuspids

   2. on either side of incisors

   3. pointed crowns

   4. for ripping and tearing

3. premolars and molars

   1. posterior and lateral to canines

   2. broad crown with rounded projections —> cusps

   3. for grinding

what are primary dentition / deciduous teeth

baby teeth

how many deciduous teeth are there

20 total

• 4 incisors

• 2 canines

• 4 molars

in each mandible and maxilla

what are secondary dentition

permanent / adult teeth

where are the permanent teeth located

above primary dentition in maxilla and below in mandible

how do permanent teeth erupt

the teeth enlarge around 6 y/o and press into deciduous teeth

how many permanent teeth are there

32 total

• 4 incisors

• 2 canines

• 4 premolars

• 6 molars

in mandible and maxilla

what are the basic digestive functions

1. most fundamental — take food into body and break it down into its basic component nutrients

2. taking in water and electrolytes via diet and delivering to the blood

   1. fluid, electrolytes, acid-base homeostasis

3. ingesting vitamins and minerals

4. producing hormones

5. excreting metabolic wastes

what are the basic digestive processes that carry out the functions

1. ingestion of food and water into digestive system via mouth

2. secretion of mucus, enzymes, acid and hormones by endocrine and exocrine glands to aid other digestive processes

3. propulsion of ingested food and liquids that pass from one digestive organ to the next

   1. accomplished by peristalsis

   2. aided by mucus

4. digestion —> food breakdown

   1. mechanical

   2. chemical (enzymatic hydrolysis)

5. absorption —> nutrients move through the wall into blood or lymphatic vessels

   1. water, electrolytes and vitamins also move into blood

6. defecation —> materials that are not digestible or usable by body continue their transit through alimentary canal until they exit as feces

what is/are the peritoneal membranes

largest serous membrane in body that folds on itself

what are the two layers of the peritoneal membrane

1. outer parietal peritoneum

   1. lines inner surface of body wall

2. inner visceral peritoneum (serosa)

   1. forms outer tissue layer of organs

what does the peritoneal cavity contain

serous fluid

what are the intraperitoneal organs almost completely covered in

visceral peritoneum

where do retroperitoneal organs sit and are they covered with peritoneum

sit outside of parietal peritoneum

only partially covered by peritoneum

what are the retroperitoneal organs

adrenal glands

aorta and IVC

duodenum (2nd - 4th parts)

pancreas

ureters

colon (descending / ascending)

kidneys

esophagus (thoracic)

rectum

what is the mesentery

double-layer peritoneum, continuous to visceral and parietal peritoneum

what does the mesentery do

• supports and bonds some organs together

  • keep small intestine in a particular shape

• houses blood vessels, nerves and lymphatic vessels

  • anchors them in place

what does the mesentery (mesentery proper) connect

mesentery to small intestine

what does the mesocolon connect

mesentery to much of the large intestine

• transverse colon

• sigmoid colon

what does the mesoappendix connect

the mesentery to the appendix

what is the omentum

double-layer fold of peritoneum

from stomach and duodenum to adjacent organs

describe the greater omentum

• 4 layers of folded visceral peritoneum

• extends from base of stomach (& duodenum) down into pelvis folding back attaching to transverse colon

• supplied by R/L gastro-omental arteries

describe the lesser omentum

• smaller, double layer

• extends from lesser curvature of stomach (and part of duodenum) to liver

• portal triad found within

what is the peritoneal ligament

double layer of peritoneum

what is the purpose of the peritoneal ligament

connects organs to organs or organs to abdominal wall

function of the falciform ligament (peritoneal ligament)

connects liver to anterior abdominal wall

function of coronary ligament (anterior and posterior) (peritoneal ligament)

attaches the superior surface of the liver to the inferior surface of the diaphragm

function of the triangular ligament (left and right) (peritoneal ligament)

left —> attaches left lobe of liver to the diaphragm

right —> attaches right lobe of liver to the diaphragm

function of hepatogastric ligament (peritoneal ligament)

liver connects to stomach

function of hepatoduodenal ligament (peritoneal ligament)

liver connects to duodenum

function of gastrosplenic ligament (peritoneal ligament)

stomach connects to spleen

function of splenorenal ligament (peritoneal ligament)

spleen connects to kidneys