Digestive anatomy

What is the abdominal cavity and how is it bounded?

The space containing the abdominal organs, bounded anterolaterally by musculo-aponeurotic walls and superiorly by the diaphragm at the 4th intercostal space

Which organs in the upper abdomen are protected by the rib cage?

Spleen, liver, stomach, and parts of the kidneys

What imaginary plane separates the abdominal cavity from the pelvic cavity?

The pelvic inlet, which divides the greater (false) pelvis above from the lesser (true) pelvis below

Which organs does the greater pelvis protect?

Portions of the ileum, cecum, appendix, and sigmoid colon

How are the four abdominal quadrants defined?

By the median plane (xiphoid to pubic symphysis) and the transumbilical plane (through the umbilicus)

Name the four abdominal quadrants.

Right upper quadrant (RUQ), left upper quadrant (LUQ), right lower quadrant (RLQ), left lower quadrant (LLQ)

Which organs are found in the right upper quadrant?

Right liver lobe, gallbladder, head of pancreas, first to third parts of duodenum, right colic (hepatic) flexure

Which organs are in the left upper quadrant?

Left liver lobe, stomach, spleen, body of pancreas, left colic (splenic) flexure

What structures are located in the right lower quadrant?

Ascending colon, cecum, appendix, and lower portion of the right kidney

What is found in the left lower quadrant?

Descending colon, sigmoid colon, and lower portion of the left kidney

Which additional structures can be present in the lower quadrants?

Ureters and internal reproductive structures (ovaries/uterus in females

How are the nine abdominal regions defined?

By two vertical midclavicular lines and two horizontal planes (subcostal and transtubercular)

Where are the midclavicular lines drawn?

Vertically from the midpoint of each clavicle down to the groin

What is the subcostal plane?

The horizontal line just below the 10th rib costal cartilages at approximately L3

What is the transtubercular plane?

The horizontal line passing through the iliac tubercles and the body of L5

What alternative plane can define the superior boundary of the nine regions?

The transpyloric plane at L1, midway between the manubrium and pubic symphysis

Which landmark structures lie on the transpyloric plane?

Pylorus of the stomach, hila of the kidneys, fundus of the gallbladder, neck of pancreas, transverse colon, duodenojejunal junction, superior mesenteric artery, and hepatic portal vein

What organs occupy the epigastric region?

Upper portion of the stomach, parts of the esophagus, liver, pancreas, duodenum, and spleen

Which organs are in the umbilical region?

Most of the small intestine, part of the large intestine, pancreas, and parts of both kidneys

What does the hypogastric (suprapubic) region contain?

Sigmoid colon, urinary bladder, rectum, and reproductive organs (uterus/ovaries or prostate)

What is found in the right hypochondriac region?

Right liver lobe, gallbladder, parts of large and small intestine, and portions of the right kidney

Which organs lie in the left hypochondriac region?

Spleen, parts of left kidney, stomach, pancreas, and colon

What structures are located in the right lumbar region?

Lower parts of liver and gallbladder, right kidney, and ascending colon

What structures are located in the left lumbar region?

Portions of the descending colon and left kidney

What is found in the right inguinal (iliac) region?

Appendix and cecum

What is found in the left inguinal (iliac) region?

Descending colon and sigmoid colon.

What are the two compartments of the oral cavity?

The oral vestibule (between teeth/gingiva and lips/cheeks) and the oral cavity proper (bounded by dental arches and palate)

What is the oral fissure?

The opening between the lips through which food enters the mouth

What role do the lips play during chewing?

They act as valves to keep food inside the oral cavity and also aid in speech, breathing, and facial expressions

What is the vermilion border?

The outer edge of the lips marking the transition between facial skin and the lip’s red transitional zone

Where does the philtrum extend?

From the midline of the upper vermilion border to the nasal septum

Which arteries supply the lips?

The superior and inferior labial arteries, branches of the facial artery, anastomosing in the midline

How are the lips innervated?

Upper lip by superior labial branches of the infraorbital nerve (V2), lower lip by inferior labial branches of the mental nerve (V3)

Where do the lips drain lymphatically?

Medial lower lip to submental nodes

What are the two types of gingiva?

Unattached (alveolar mucosa) which is loose and red, and attached gingiva (gingiva proper) which is pale and firmly bound to bone

How many permanent teeth does an adult have and what are their types per side?

32 total: 2 incisors, 1 canine, 2 premolars, and 3 molars on each side of both jaws

What are the three parts of a tooth?

Crown (visible), neck (at gum line), and root (in tooth socket)

What is found inside the pulp cavity?

Blood vessels, nerves, and connective tissue

What covers dentin on the crown and on the root?

Enamel covers the crown

What type of joint is formed between tooth cementum and alveolar bone?

A gomphosis (dento-alveolar syndesmosis) via the periodontium

Which arteries supply the lower teeth and their buccal gingiva?

Branches of the inferior alveolar artery from the maxillary artery

Which arteries supply the upper teeth and their buccal gingiva?

Posterior superior alveolar artery (from maxillary) and anterior superior alveolar artery (from infraorbital)

How are the upper palatal gingiva and anterior hard palate innervated?

Palatal gingiva by greater and lesser palatine nerves

Which nerves supply the lower teeth and buccal and lingual gingiva?

Inferior alveolar nerve (teeth), mental and buccal nerves (buccal gingiva), and lingual nerve (lingual gingiva) from V3

What bones form the hard palate?

Palatine processes of the maxilla anteriorly and horizontal plates of the palatine bones posteriorly

Which foramina transmit the palatine arteries and nerves?

Greater palatine foramen (greater palatine vessels/nerves) and lesser palatine foramen (lesser palatine vessels/nerves)

What defines the fauces (isthmus) of the oral cavity?

Passage bounded by soft palate, tongue, palatoglossal arches anteriorly, and palatopharyngeal arches posteriorly containing the palatine tonsils

Which artery is the main arterial supply to the palatine tonsils?

The tonsillar branch of the facial artery

Name the muscles of the soft palate and their primary actions.

Tensor veli palatini tenses the palate and opens the auditory tube

What arteries supply the palate?

Descending palatine artery (greater and lesser palatine branches) from the maxillary artery, and the palatine branch of the ascending palatine artery from the facial artery

How is the sensory innervation of the palate arranged?

Greater palatine nerve for most hard palate, lesser palatine nerve for soft palate, and nasopalatine nerve for anterior hard palate (all from V2).

What are the primary functions of the tongue?

Speech articulation, taste perception, bolus formation and propulsion during swallowing, food manipulation during mastication, and oral cleansing

Into which three anatomical regions is the tongue divided?

Root (posterior third), body (anterior two-thirds), and apex (tip)

What structures bound the root of the tongue?

Hyoid bone, epiglottis, soft palate, and mandible

What surfaces does the tongue have?

A superior (dorsum) surface and an inferior (underside) surface separated by its margins

What landmark divides the dorsum of the tongue into anterior and posterior parts?

The V-shaped terminal sulcus, with its apex pointing to the foramen cecum

What is the foramen cecum?

A remnant of the embryonic thyroglossal duct located at the tip of the terminal sulcus

Which lingual papillae contain taste buds?

Vallate, foliate, and fungiform papillae (filiform papillae lack taste buds)

Where are the vallate papillae located?

In a row just anterior to the terminal sulcus, surrounded by trenches containing taste buds

What is the role of filiform papillae?

Provide a rough surface for mechanical processing and contain touch receptors but no taste buds

What is the frenulum of the tongue?

A midline fold of mucosa anchoring the inferior tongue to the floor of the mouth, allowing movement of the tongue tip

What opens at the sublingual caruncles on either side of the frenulum?

The openings of the submandibular (Wharton’s) ducts of the submandibular salivary glands

Which cranial nerve supplies motor innervation to almost all intrinsic and extrinsic tongue muscles?

Hypoglossal nerve (CN XII), except palatoglossus which is supplied by the pharyngeal plexus (vagus nerve)

Name the four extrinsic muscles of the tongue and their primary actions.

Genioglossus: depression, protrusion, contralateral deviation

Which nerve innervates the palatoglossus muscle?

Pharyngeal plexus of the vagus nerve (CN X)

What are the four intrinsic muscles of the tongue?

Superior longitudinal, inferior longitudinal, transverse, and vertical muscles

What action does the superior longitudinal muscle perform?

Shortens the tongue and curls the apex and sides upward

What action does the inferior longitudinal muscle perform?

Shortens the tongue and curls the apex and sides downward

What do the transverse and vertical intrinsic muscles do?

Transverse: narrow and elongate the tongue

Which nerve provides general sensory innervation to the anterior two-thirds of the tongue?

Lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V3)

Which nerve carries taste fibers from the anterior two-thirds of the tongue?

Chorda tympani branch of the facial nerve (CN VII), via the lingual nerve

Which nerve supplies both general and special sensation to the posterior one-third of the tongue?

Glossopharyngeal nerve (CN IX)

What supplies the small area of general and some taste sensation just anterior to the epiglottis?

Internal laryngeal branch of the vagus nerve (CN X)

What is the arterial supply of the tongue?

Lingual artery, a branch of the external carotid artery

How is venous blood from the tongue drained?

Via the lingual veins into the internal jugular vein

To which lymph nodes does lymph from the tongue drain?

Superior and inferior deep cervical nodes, as well as submandibular and submental nodes.

What are the three main pairs of salivary glands?

Parotid, submandibular, and sublingual glands

Where are accessory salivary glands located?

Scattered in the palate, lips, cheeks, tonsils, and tongue

What are the primary functions of saliva?

Hydrates oral mucosa, lubricates food, begins starch digestion (amylase), and provides antimicrobial action (e.g., hydrogen peroxide)

Which enzyme in saliva begins starch digestion?

Amylase

Why is saliva called “nature’s mouthwash”?

Because it contains antimicrobial compounds like hydrogen peroxide that help clean the mouth

Which salivary gland is the largest?

The parotid gland

Where does most of the parotid gland lie?

In the retromandibular fossa, anteroinferior to the external acoustic meatus

Between which structures is the parotid gland wedged?

Between the ramus of the mandible and the mastoid process/SCM muscle

What fascia forms the parotid sheath?

The investing layer of the deep cervical fascia

Which nerve trunk passes through the parotid gland without innervating it?

The extracranial portion of the facial nerve (parotid plexus)

Which vessels are enclosed within the parotid gland?

The retromandibular vein and the external carotid artery

Which nerve and artery traverse the superior part of the parotid gland?

Auriculotemporal nerve and superficial temporal artery

Describe the course of the parotid (Stensen’s) duct.

Runs over the masseter, turns medially at its anterior border, pierces the buccinator, and opens opposite the second maxillary molar

What provides sensory innervation to the parotid gland?

Auriculotemporal nerve (V3) and great auricular nerve (cervical plexus)

Which nerve carries parasympathetic fibers to the parotid gland?

Glossopharyngeal nerve via the otic ganglion and auriculotemporal nerve