A & P Exam 2

Alimentary canal

The gastrointestinal tract through which food passes, starting from the mouth and ending at the anus, consisting of organs such as the esophagus, stomach, and intestines.

Gastrointestinal (GI) Tract

The organ system responsible for the digestion and absorption of food, begins with the mouth and continues through the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine which opens to the exterior through the anus.

Accessory organs of the Digestive system

along the length of the GI tract, several accessory structures produce secretions containing water, enzymes, buffers and other components that assist in preparing organic and inorganic nutrients for absorption. Such as the liver, pancreas, and gallbladder.

The four layers of the alimentary canal

include the mucosa, submucosa, muscularis, and serosa. These layers play vital roles in digestion and absorption.

Mucosal layer of GI tract

the innermost layer of the GI tract that contains Stratified squamous epithelium – (found in the oral cavity, pharynx, the upper portions of the esophagus, and rectum). and Simple columnar epithelium – (found within the lower portions of the esophagus, the stomach, small intestine, and most of the large intestine.  Possess numerous goblet cells (mucous producing cells).) responsible for secretion and absorption.

Lamina propria layer of mucosal layer

a basement membrane composed of areolar connective tissue.  Contains blood vessels, sensory nerve endings, lymphatic vessels, scattered areas of lymphoid tissue (recall Peyer’s patches and MALT), and mucous glands

Muscularis mucosae layer of mucosal layer

two concentric layers of smooth muscle.  The inner layer encircles the lumen (circular layer) and the outer layer runs parallel to the long axis of the GI tract (longitudinal layer).  Contractions of the muscles within the muscularis mucosae create the folds that project from the internal surface of the GI tract such as rugae, plicae circularis, and villi.

Submucosal layer of GI tract

a layer of dense irregular connective tissue surrounding the mucosa.  Contains large blood vessels, lymphatic vessels, nerves, and in some regions, exocrine glands that secrete enzymes and buffers into the lumen of the GI tract.

Muscularis externa of GI tract

dominated by smooth muscle oriented in two layers:  an inner circular layer and an outer longitudinal layer.  These layers are essential in the mechanical processing of food and the propulsion of food through the digestive tract.

Myenteric Plexus (plexus of Auerbach)

A network of nerves located between the layers of the muscularis externa, responsible for motility, especially the rhythm and force of the contractions of the muscularis. 

Submucosal plexus (Plexus of Meissner)

A network of nerves found in the submucosal layer of the GI tract, responsible for regulating digestive secretions and reacting to the presence of food

Digestive system blood vessels functions

1. They transport the protein and carbohydrate nutrients absorbed by mucosal cells after food is digested in the lumen. Lipids are absorbed via lacteals, tiny structures of the lymphatic system. 

2. The blood vessels’ second function is to supply the organs of the alimentary canal with the nutrients and oxygen needed to drive their cellular processes.

Peritoneum

A serous membrane that lines the abdominal cavity and covers the abdominal organs. It plays a crucial role in protecting and supporting the organs, as well as facilitating movement.

Serosa

The outermost layer of the GI tract, consisting of connective tissue and epithelium, providing protection and support for the abdominal organs.

Mesentery

A fold of peritoneum that attaches the intestines to the abdominal wall, providing support and containing blood vessels, lymphatics, and nerves.

Greater omentum

A large fold of peritoneum that hangs down from the stomach and drapes over the intestines, providing insulation, cushioning for abdominal organs, and serving as an immune response site.

Falciform Ligament

A ligament that extends from the liver to the anterior abdominal wall, separating the right and left lobes of the liver and supporting its position.

Lesser omentum

A double layer of peritoneum that extends from the liver to the lesser curvature of the stomach, playing a role in supporting the stomach and providing a pathway for blood vessels and ducts.

Mesocolon

A fold of peritoneum that attaches the colon to the posterior abdominal wall, supporting its position and facilitating the passage of blood vessels and nerves.

Ingestion

The process of taking food and liquids into the body through the mouth, which is the first step of digestion.

Mechanical processing

chewing, mixing of food with saliva, churning of food in the stomach and segmentation in the intestine.

Segmentation

The process of rhythmic contractions of the circular muscles in the intestine that mix food with digestive juices and enhance nutrient absorption.

Propulsion

The process of moving food through the digestive tract, which includes swallowing and the wave-like involuntary muscle contractions known as peristalsis.

Chemical digestion

the chemical and enzymatic breakdown of foods into small organic molecules that can be absorbed such as carbohydrates, proteins and lipids.

Secretion

emission of water, enzyme, buffers, and acids into the lumen.

Absorption

movement of small organic end products and other important molecules (such as water, electrolytes, carbohydrates, proteins, lipids, nucleic acids, vitamins, and minerals like Fe or Ca) from the lumen of the GI tract into the interstitial fluids, blood, or lymph.

Compaction

the progressive dehydration of indigestible materials and organic wastes prior to elimination from the body. The compacted materials are called feces and the elimination of feces via the anus is called defecation

Neural control of the GI tract

The walls of the alimentary canal contain a variety of sensors that help regulate digestive functions. These include mechanoreceptors, chemoreceptors, and osmoreceptors, which are capable of detecting mechanical, chemical, and osmotic stimuli, respectively.

Hormonal control of the GI tract

1. The main digestive hormone is Gastrin- is secreted by the stomach in response to the presence of food. Gastrin stimulates the secretion of gastric acid by the parietal cells of the stomach mucosa. 

2. secretin- produced by the duodenum stimulates a watery secretion of bicarbonate by the pancreas

3. Cholecystokinin (CCK) - stimulates the secretion of pancreatic enzymes and bile from the liver and release of bile from the gallbladder

4. gastric inhibitory peptide (GIP) - inhibits gastric secretion and slows gastric emptying and motility.

Mouth

lined with non-keratinized stratified squamous; produces the bolus

Bolus

A mass of chewed food that is formed in the mouth and prepared for swallowing.

Labia

lips, possess no sweat glands or sebaceous glands.  Distinguished by the red margin and the orbicularis oris muscle.  A superior and inferior labial frenulum attaches the lips to the gums.

Cheeks

The lateral walls of the mouth, formed by the buccinator muscles and covered by skin on the outside and mucous membrane on the inside.

Vestibule (of the oral cavity)

area bounded by the lips and cheeks externally and internally by the Gingivae (gums) and teeth.

Hard Palate

The bony anterior part of the roof of the mouth, separating the oral cavity from the nasal cavity, covered by mucous membrane. composed of the palatine process of the maxilla and the palatine bones.

Soft palate

The flexible, muscular posterior part of the roof of the mouth that separates the oral cavity from the nasopharynx, playing a key role in swallowing and speech. Composed of muscle tissue rather than bone

Uvula

composed of connective and reticular tissue; helps to prevent food from entering the oropharynx prematurely and houses WBCs.

Palatine tonsils

lie on either side of the oral cavity in the archways called the fauces.

Root of the tongue

the fixed portion of the tongue that enters into the oropharynx.  Differentiated from the body of the tongue by the v-shaped circumvallate papillae.  Possesses the lingual tonsils.

Body of the tongue

the movable portion of the tongue that is primarily responsible for speech and swallowing. It is covered with taste buds and plays a role in the chewing process.

Geniohyoid and Myolohyoid muscles

muscles located in the floor of the mouth, aiding in tongue movement and stabilizing the hyoid bone.

Taste buds

sensory structures located on the tongue responsible for detecting flavors. They are involved in the perception of taste and contribute to the overall experience of flavor.

Lingual papillae

small, nipple-like projections on the surface of the tongue that contain taste buds and enhance surface texture.

Filiform Papillae

hair-like papillae scattered all over the anterior 2/3 of the tongue.  They do not have taste buds associated with them.  These are designed to create friction on the surface of the tongue.

Foliate papillae

4-5 vertical folds located on the lateral margins of the posterior region of the tongue.  Each papillae of this type possesses many taste buds.   

Circumvallate papillae

7 to 12 relatively large, round papillae shaped like the tip of a pencil eraser surrounded by deep epithelial folds.  These are found on the posterior margin of the tongue in a V pattern. Each circumvallate papilla possesses about 100 taste buds along the sides of each papilla.

Fungiform Papillae

mushroom-shaped papillae within shallow depressions scattered over the anterior 2/3 surface of the tongue. These typically possess only 5 taste buds located on the tops of each papilla.

Salivary Glands

<span>Exocrine glands that secrete saliva into the oral cavity. They play a crucial role in digestion, oral hygiene, and taste sensation, with major glands including the parotid, submandibular, and sublingual glands.

Salivary Glands functions

1. Moistens and lubricates the mouth and food; 

2. Cleanses food by defensins, lysozymes, and IgA antibodies; 

3. Dissolves food chemicals for gustation;

4. Initiates chemical digestion of complex carbohydrates by salivary amylase and fats by lingual lipase.

3 types of salivary glands

Parotid Salivary Glands

The largest salivary glands located near the ears, contains only serous cells for the production of salivary amylase, lysozymes, and IgA antibodies.  Secrete into the parotid duct to the oral cavity.  innervated by CN VII (facial nerve)

Sublingual salivary glands

Smallest salivary glands located beneath the tongue, contains mostly mucous cells and produces a watery mucin to act as a buffer and lubricant.  Secrete into the sublingual ducts.  innervated by CN IX (glossopharyngeal nerve).

Submandibular salivary glands

Located beneath the jaw, equal numbers of serous cells and mucous cells and therefore secrete a mixture of mucin and salivary amylase.  Secrete into the submandibular ducts.  innervated by CN IX (glossopharyngeal nerve).

Teeth

Structures in the mouth used for biting and chewing food. They include incisors, canines, premolars, and molars, each serving specific functions in the digestive process.

Primary dentition or Deciduous teeth

The first set of teeth that develop in children, typically consisting of 20 teeth that eventually fall out and are replaced by permanent teeth.

Secondary Dentition (permanent teeth)

The second set of teeth that emerge in adults, usually comprising 32 teeth in total, which replace the primary dentition and are intended to last a lifetime.

Incisors (perm teeth)

blade-shaped teeth at the front of the mouth; for cutting and nipping; possess a single root; 8 total (4 on top/4 on bottom) described as either central or lateral incisors.

Canine (Perm teeth)

conical-shaped with a sharp ridgeline and pointed tip; for tearing and piercing; possess a single root; sometimes called cuspids or eyeteeth; 4 total (2 on top/2 on bottom)

Premolars (perm teeth)

flattened crowns with prominent ridges; for grinding, mashing and crushing; possess one or two roots; sometimes called bicuspids; 8 total (4 on top/4 on bottom) described as either 1st or 2nd premolars.

Molars (perm teeth)

flattened crowns with prominent ridges; for grinding and crushing; typically possess three or more roots; 12 total (6 on top/6 on bottom) described either as 1^st, 2^nd, or 3^rd molars.  The 3^rd molars are sometimes called wisdom teeth.

Crown

The visible part of a tooth above the gumline, typically covered by enamel and involved in chewing.

Enamel

The hard, outer layer of a tooth that protects it from decay and damage. It is the most mineralized and hardest substance in the human body.

Dentin

The dense, bony tissue beneath the enamel that forms the bulk of a tooth and provides structural support. It contains microscopic tubules that communicate with the pulp.

Pulp (teeth)

The soft tissue inside a tooth that contains nerves, blood vessels, and connective tissue, responsible for nourishing the tooth and providing sensation.

Neck (teeth)

The region of a tooth located between the crown and the root, where the enamel meets the cementum.

Root (Teeth)

The part of the tooth that is embedded in the jawbone, anchoring the tooth in place and containing the tooth's nerve and blood supply.

Gingivae

The gum tissue surrounding the teeth, providing support and protection for the roots and underlying structures.

Alveoli (teeth)

The sockets in the jawbone that hold the roots of the teeth, providing structural support.

Cementum

The calcified tissue covering the root of a tooth, aiding in anchoring the tooth to the jawbone through the periodontal ligament.

Periodontal Ligament

The connective tissue that surrounds the roots of the teeth, anchoring them to the alveolar bone and allowing for slight movement during chewing.

Canal (teeth)

The narrow passageway within the tooth that houses the dental pulp, nerves, and blood vessels.

Apical Foramen (Teeth)

The opening at the tip of the tooth root through which nerves and blood vessels enter the tooth, connecting it to the body's circulatory system.

Nasopharynx

The upper part of the pharynx, located behind the nose and above the soft palate, that serves AIR and only AIR as an airway passage and is involved in the respiratory system. Lined with pseudostratified columnar epithelium and houses the Pharyngeal (Adenoid) tonsils.

Pharyngeal (Adenoid Tonsils when enlarged)

Lymphoid tissues located in the nasopharynx that play a role in immune response by trapping pathogens that enter through the nasal cavity.

Oropharynx

extends between the soft palate and the level of the hyoid bone.  At the boundary between the nasopharynx and the oropharynx, the epithelial tissue changes from pseudostratified columnar to stratified Squamous epithelium; accommodates the movement of food through this region and protects against abrasion.

Laryngopharynx

includes the portion of the pharynx between the hyoid bone and the entrance to the larynx and esophagus.  Like the oropharynx, the laryngopharynx is lined with Stratified Squamous epithelium.

Esophagus

a hollow muscular tube that functions to carry bolus from the pharynx to the stomach; passes through an opening in the diaphragm called the esophageal hiatus.

Esophageal Hiatus

The opening in the diaphragm through which the esophagus passes, allowing for the passage of food from the throat to the stomach.

Composition of upper 3rd of Esophagus

composed of skeletal muscle

Composition of middle 3rd of Esophagus

mixture of skeletal and smooth muscle

Composition of Lower 2/3 of esophagus

composed of smooth muscle that facilitates peristalsis in food processing.

What type of epithelium is the upper portion of the esophagus lined with?

Stratified squamous epithelium

What type of epithelium is the lower portion of the esophagus lined with?

Simple columnar epithelium

Esophageal Glands

mucous glands that help lubricate the esophagus and protect its lining.

Peristalsis

The coordinated, wave-like muscle contractions that move food through the digestive tract.

Upper esophageal sphincter

A ring of muscle that controls the passage of food from the pharynx to the esophagus, preventing backflow.

Cardiac/ gastroesophageal/ lower esophageal sphincter

A ring of muscle at the junction of the esophagus and stomach that prevents the backflow of stomach contents into the esophagus.

Deglutition

The process of swallowing food and liquids from the mouth through the pharynx and into the esophagus.

oral phase of Deglutition

The initial phase of swallowing where food is chewed and mixed with saliva, forming a bolus to be pushed to the pharynx. ; voluntary

Pharyngeal phase of Deglutition

The phase of swallowing where the bolus is pushed from the oropharynx into the esophagus, triggered by sensory receptors in the pharynx.; involuntary and controlled by autonomic nervous system

Esophageal phase of Deglutition

The final phase of swallowing where the bolus travels down the esophagus to the stomach, facilitated by peristaltic contractions. ; involuntary

Peritoneum

A serous membrane that lines the abdominal cavity and covers the organs within it, providing support and facilitating movement.

Visceral peritoneum

The membrane that covers the organs within the abdominal cavity, providing protection and support.

Parietal peritoneum

The layer of the peritoneum that lines the inner walls of the abdominal cavity, distinct from the visceral peritoneum which covers the organs.

Stomach

A muscular organ involved in the digestion of food, located between the esophagus and the small intestine. Converts the bolus into chyme

Chyme

A semi-liquid mixture of partially digested food and gastric juices that forms in the stomach and moves into the small intestine.

Cardiac region (cardia) (stomach)

The area of the stomach where the esophagus connects, involved in entry of food into the stomach.

Gastroesophageal Junction

serves as the junction between the esophagus and stomach and prevents backflow of stomach contents into the esophagus.

Fundus

The upper part of the stomach that stores undigested food and gases released during digestion.

Body (stomach)

the largest region of the stomach; area between the fundus and the curve in the J; functions as a mixing bowl for ingested food and secretions from the walls.