ANATOMY - Term Test 5 (Digestive System) Flashcards
The organs of the digestive system together perform a vital function, which is:
preparing nutrients for absoprtion and for use by the body
Digestion
The complete process of altering the physical and chemical composition of ingested food material so that it can be absorbed and used by body cells
Main organs of the digestive system form a tube that goes all the way through the _______ cavities of the body, and opens at both ends. This tube is called:
ventral
alimentary canal/digestive tract/gut
Gastrointestional (GI) tract
refers ONLY To the stomach and intestines (somtimes used in reference to entire alimentary canal)
Upper digestive tract structures
Mouth
Pharynx
Esophagus
Stomach
Lower digestive tract structures
- small intestine: duodenum, jejunum, ileum
- large intestine
- cecum
- colon: ascending colon, transverse colon, descending colon, sigmoid colon
- rectum
- Anal canal
Accessory organs of the digestive system (10)
- Salivary glands
- Parotid
- Submandibular
- Sublingual
- Tongue
- Teeth
- Liver
- Gallbladder
- Pancreas
- Vermiform appendix
Provide the length (or range of length) of the following:
Upper digestive tract
Small intestine
Large intestine
Upper digestive tract: 0.5m
Small intestine: 6 - 8 m
Large intestine: 1.5 - 1.8 m
True or False. The digestive tract is outside of the internal environment of the body
True. The digestive tube itself passes through the ventral body cavities but it is really outside the body’s internal environment.
How many layers are in the GI tract?
4 layers
1) mucous lining
2) submucous coat of connective tissue with main blood vessels of the tract embedded in them
3) muscular layer
4) fibroserous layer
Mesentery
Large, fanlike fold of serous membrane (projection of the parietal peritoneum) that connects GI tract to the abdominal wall (connects the parietal and visceral portions)
This is where blood vessels and nerves travel through to reach GI tract; allows free movement of each coil of the intestine and helps prevent strangulation of the long tube
From outside to inside, what are the layers of the GI tract?
serosa, muscularis, submucosa, mucosa
Mucosa
- innermost layer of GI wall (faces the lumen of the tube)
- made of three layers:
- mucous epithelium (inner)
- lamina propria - loose layer of fibrous connective tissue
- muscularis mucosae - thin layer of smooth muscle
Submucosa
- composed of connective tissue that’s thicker than mucosal layer
- contains numerous small glands, blood vessels, and parasympathetic nerves that form the submucosal plexus (Meissner plexus)
Muscularis
- thick layer of muscle tissue that wraps around submucosa
- has an inner layer of circular smooth muscle and an outer layer of longitudinal smooth muscle
- contains nerves organized into a plexus (Myenteric plexus or Auerbach plexus) - lies between the two muscle layers
The Meissner and Auerbach plexuses are collectively called ___________ and comprise the major part of the ________ nervous system.
What important role to these plexuses play?
intramural plexus; enteric nervous system (ENS)
Role: regulation of digestive tract movement and secretion
Serosa
- outermost layer of GI wall
- made up of serous membrane
- actually the visceral layer of the peritoneum (the serous membrane that lines the abdominopelvic cavity and covers its organs)
True or False. The four layers that form the GI tract wall stay consistent in structure throughout the entire tract.
False. It’s the same four layers BUT their structures vary in different regions of the tube throughout its length
How are the esophagus wall layers modified?
- Mucosa layer: stratified squamous epithelium (resists abrasion)
- two muscle layers:
- inner one is circular fibers
- outer is longitudinal fibers
- striated muscle in upper part and smooth muscle in lower part of esophagus and rest of tract
- Serosa: outer layer, fibrous
How are the stomach wall layers modified?
- Mucosa layer: arranged in flexible longitudinal folds (rugae); allow for distension; also has gastric pits with glands
- Muscular layer: has 3 layers instead of just 2
- circular, longitudinal, and oblique fibers
- two sphincters:
- lower esophageal sphincter (LES) - at entrance of stomach
- pyloric sphincter: stomach exit
- Serosa: outer layer is visceral peritoneum, hands in a double fold from the lower edge of the stomach over the intestines (forms an apron-like structure)
- greater omentum (folds) and lesser omentum (connects stomach to liver)
The mouth is also called the
oral cavity/buccal cavity
Structures that form the oral cavity
- lips (surround the orifice of the mouth and form anterior boundary of the oral cavity)
- cheeks (side walls)
- tongue and its muscles (floor)
- hard palate and soft palate (roof)
Lips are covered externally by __________ and internally by __________ that continues into the oral cavity and lines the mouth.
skin; mucous membrane
Define the following terms related to the lips.
1) Philtrum
2) Tubercle
3) Oral Fissure
1) Philtrum: near the midline of the upper lip, markekd by a shallow vertical groove (think where your cupid’s bow is, piltrum is smack dab in the middle of it); ends at the tubercle (junction between skin and mucous membrane)
2) Tubercle: a slight prominence where the skin and mucous membrane meet (think where the plump part of your lips are)
3) oral fissure: the line of contact between the lips when they are closed
Function of the lips
- keeps food in the mouth when chewing
- senses temperature and food textures before it enters the mouth
- involve with speech sounds (syllables)
Cheeks
- form the lateral boundaries of the oral cavity
- continuous with the lips (in front), lined by mucous membrane that is reflected onto the soft palate and alveolar process of each jaw (forming the gums/gingiva)
- has mucus-secreting glands between mucous membrane and buccinator muscles
Walls of the cheeks are formed in large part by which muscle?
buccinator
Hard palate composition
4 bones: two maxillae, two palatines
Soft palate
- forms a partition between mouth and nasopharynx
- made by muscles arranged in an arch shape
- opening of the arch leads from mouth into oropharynx (called fauces)
- midpoint of the posterior border of the arch is the uvula
Tongue
solid mass of skeletal muscle components (intrinsic muscles) covered by a mucous membrane
Components of the tongue
blunt root, tip, and central body
Upper/dorsal surface of the tongue is what colour and covered by what?
moist, pink, and covered by papillae (rough elevations)
papillae has sensory organs (taste buds)
What are the four types of papillae?
all located on the sides or upper surface of tongue
1) circumvallate: 10-14 large mushroom like papillae that run across the tongue in an inverted v-shape; taste buds located on the sides of the papillae
2) fungiform: found on sides and tips of tongue; taste buds located on the sides of these ones
3) foliate: leaflike ridges on te posterior lateral edges of the tongue, also has taste buds
4) filiform: many of these (distributed over anterior 2/3 of tongue); filamentous and threadlike; NO taste buds
Lingual frenulum
fold of mucous membrane in the midline of the undersurface of the tongue
helps anchor the tongue to the floor of the mouth
Ankyloglossia
congenital condition where the lingual frenulum is too short and hinders tongue movement causing the person to be described as “tongue tied” and have faulty speech
Fimbriate fold (plica fimbriata)
fold of mucous membrane that extends towards the apex of the tongue on either side of the lingual frenulum
Why is it beneficial for drugs to be place sublingually (i.e. what anatomical structures allow for this to be beneficial)?
There are many vessels that are extremely superficial and covered only by a very thin layer of mucous (including deep lingual vein). This makes drugs such as ASA or NTG to be quickly absorbed into the circulation rapidly
Changes in size and shape of the tongue caused by intrinsic muscle contraction assists with what functions?
1) mastication - the muscles assist in placing food material between teeth so that you can chew
2) speech formation - syllables
Why does the tongue have extreme maneuverability?
Because the intrinsic muscles that make up the tongue have their muscle fibers oriented in all directions
Contraction of extrinsic tongue muscles (i.e. those that insert into the tongue buy have an origin on some other structure) allow for what functions?
1) Deglutition (swallowing)
2) Speech
The salivary glands are located (inside/outside) the alimentary canal and provide their exocrine secretions through ______________.
outside
via ducts (from glands into lument of GI tract)
What do the serous cells and mucous cells secrete in the salivary glands?
Serous cells produce a watery secretion that has digestive enzymes
Mucous cells produce mucus
What are the three pairs of major salivary glands?
1) parotid
2) submandibular
3) sublingual
How much saliva gets produced daily?
1 L
Name the minor salivary glands, and how much (total %) do they contribute to the total salivary volume?
Minor salivary glands: buccal, lingual, palatine, labial, molar glands
Contribute <5% of total salivary volume but is important for the hygiene and comfort of the mouth tissues + digestive enzyme production
Parotid glands
- largest of the paired salivary glands
- located between skin and underlying masseter muscle in front of and below external ear
- produce a watery (serous) type of saliva containing enzymes (NO MUCUS)
Parotid ducts
- aka Stensen ducts
- ~5cm (2 inch) long
- penetrate the buccinator muscle on each side and open into the mouth through parotid papilla
Inflammation of the parotid glands is known as what, and it is caused by _____________.
called: mump/parotitis
cause: paramyxovirus
Submandibular glands
- aka mixed/compound glands
- contain both serous (enzyme) and mucus producing elements
- located just below mandibular angle
- irregular shape, size of a walnut
*
Wharton ducts
- ducts of the submandibular gland, opens into the mouth on either side of the lingual frenulum
Sublingual glands
- smallest of the main salivary glands
- lie in front of submandibular glands under mucous membrane that’s covering floor of mouth
- each sublingual gland is drained by 8-20 ducts (Rivinus ducts) that open into floor of the mouth
- produce ONLY a mucous type of saliva
The organs of mastication
teeth
The tooth is made up of 4 special types of connective tissues called ___________. They include:
dental tissues
1) Pulp: soft, fibrous connective tissue with blood vessels and nerves at the corner of each tooth
2) Dentin: hard, mineralized connective tissue similar to bone; forms the body of the tooth
3) Cementum: hard, mineralized connective tissue similar to bone; forms a coat around root of the tooth and helps connect to the jawbone
4) Enamel: hard, mineralized connective tissue; harder than bone; forms hard covering of exposed tooth surfaces
What are the three main parts of a typical tooth
crown, neck, and root
Crown
- exposed portion of a tooth
- covered by enamel (the hardest and chemically most stable tissue in the body)
Composition of enamel
- 97% calcified (inorganic) material
- 3% organic material and water
- develops as an interlocking set of rods that forms an incredibly strong coating over the crown
- withstands abrasive process of mastication
- no longer has any living cells by adult hood so cannot remodel/repair self
Root of tooth
- the part of the tooth that fits into the socket of the alveolar process of upper/lower jaw
- root is not rigidly anchored to alveolar proecss by cement, rather is suspended in the docket by periodontal membane (which has periodontal ligaments and collagen fibers)
Which of the 4 tissue layers of the tooth makes up the greatest proprtion of the tooth body?
dentin
Where is the pulp cavity of a tooh located?
covered by dentin, cavity consists of pulp tissue, blood and lymphatic vessels, and sensory nerves
Dentition
type, number, and arrangement of teeth in the jaws
of primary/deciduous teeth (baby teeth)
of permanent teeth
20 deciduous teeth
32 permanent teeth
Eruption of deciduous teeth (at what age)
- first tooth usually erupts ~6 month, and the rest follow at a rate of 1 or more a month until 20 have appeared
- deciduous teeth generally shed between 6 and 13 y. o
Third molars are also known as
wisdom teeth
If an individual does not form wisdom teeth, then the number of adult teeth would be:
28
Teeth in the upper jaw are called ___________.
Teeth in the lower jaw are called ___________.
maxillary teeth
mandibular teeth
Deciduous teeth are identified by either:
name or capital letters (A, B, C, etc.) applied in a clockwise direction
Permanent teeth are identified by:
Arabic numeral (1, 2, 3, etc.) in a clockwise direction
Deglutition
the act of swallowing which moves a rounded mass of food (bolus) from the mouth ro the stomach
Esophagus
- a collapsible, muscular, mucosa-lined tube ~25cm (10 in) long, extends from pharynx to stomach and pierces the diaphragm on the way down from thoracic to abdominal cavity
- lies posterior to the trachea and heart
- a dynamic passageway for food (i.e. food is being pushed to stomach)
- can be separated into:
- cervical part (esophagus in neck)
- thoracic part (in thorax)
- abdominal part (in abdomen)