Chapter 23 Digestive System Flashcards
1
Q
Digestive System
A
- Two groups of organs
- Alimentary Canal (Gastrointestinal GI tract)
- mouth to anus
- digests food/ absorbs fragments
- Mouth, pharynx, esophagous, stomach, small intestine, large intesitn
- Accesory Digestive organs
- Teeth, tounge, gallbladder, digestive glands
2
Q
Digestive Processes
A
- Ingestion) taking food into digestive tract (eating)
- Propulsion) moves food through alimentary canal
- swallowing) Initated voluntary
- periatalsis) Involuntary swallowing
- Mechanincal breakdown) chewing, mixing food with saliva, churning
- Segmentation) local constrictions of small intestine to mix food with digestive juices. makes absorption more efficent.
- Digestion) Catabolic reation where enzymes secreted into lumen brak down food
- Absorption) Passage of Digested end products from the lumen of GI tract into blood
- Defication) elimination of indesgtibale substances from the body
3
Q
Peritonium and Peritoneal Cavity
A
- Peritoneum) serous membrane of abdominal cavity
- Visceral Peritoneum) on external surface of most digestive organs
- Parietal Peritoneum) lines the body wall
- Peritoneal cavity) between two peritoneums
- fluid lubricates mobile organs
- Mesentary) Duble layer of peritoneusm
- sheet of two membranes fused back to back
- extends to digestive organs from the body wall
- Routes vesels and nerves to digestive organs
- Holds organs in place. Stores fat
- Mostly found dorsally, some ventral mesentary
- Retroperitoneal Organs) Posterior to peritoneum
- most of the pancreas and duodenum and parts of large intestine
- Intraperitoneal Organs) Surrounded by peritoneum
- Stomach keeps its mesentary
4
Q
Peritonitis
A
- Inflammation of the peritoneum
- causes) piercing abdominal wound, ulcer, ruptured apendix
- Treatment) removal of debris and antibiotice
5
Q
Histology of the Alimentary Canal) Mucosa
A
- Mucosa) moist epithelial membrane that lines alimentary canal lumen from mouth to anus
- Secretes mucus, digestive enzymes and hormones
- Absorbs end products of digestion
- Protects against infectious desiese
- Three Sublayers
- Epithelium) Simple columnar epitheliam rich in mucus- secreting cells
- stratified squamous epithelium in mouth, esophagous, and anus
- Mucus) Protects digestive organs from enzymes and eases food passage
- Lamina Propria) Loose areolar connective tissue
- Capalries nurish epithelium and absorb digestion nutrients
- Lymphoid Follicles) defend against microoorganisms
- Muscularis Muscosae) Layer of smooth muscle cell
- provide local movemnts of mucosa
6
Q
Histology of the Alimentary Canal) Submucosa
A
- Areolar connective tissue
- Blood and lymphatic vessels, lymphoid follicles and nerve plexus.
- Abundent elastic fibers enable stomach to regain its normal shape after temporarily storing a large meal
7
Q
Histology of the Alimentary Canal) Muscularis Externa
A
- Responsible for Segmentation and Peristalsis
- Inner circular and outer longitudinal layers
- Sphincters) circular layer thickents in some areas
- Myenteric nerve plexis located bettween two muscle layers
8
Q
Serosa
A
- Outermoast layer of intraperitonal organs is Visceral Peritoium
- Areolar CT covered with moesothelium (single layer of squamous epithelial cells)
- Serosa is replaced by fibrous dense, CT called Adventitia in esophagus
- Retropreitoneal Organs) have both an adventitia and serosa
- adventita) faces dorsal body wall
- Serosa) faces peritoneal cavity
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9
Q
Blood Supply) Splanchic Circulation
A
- Splanchnic Circulation) arteries that branch off abdominal aorta to serve digestive organs and hepatic portal circulation
- Aterial suply the branches of celiac trunk that serve spleen liver and stomach and the mesentaric aterties which serve digestive system (recive one quarter of cardiac output)
- Hepatic Portal Circulation
- Drains nutrient-rich blood from digestive organs
- Delivers to Liver for processing
10
Q
Enteric Nervous System
A
- Entric Nervous System) GI trac’ts own nervous system
- conists of over 100 million nuerons
- Steffed by enteric nuersons
- Two major Intresnsic Nervous Plexuses (ganglia ocnnected via unmyelnated tracts) found in the wall of the GI canal
- Submucosal Nerve Plexus) occupies submucosa
- Myerntric Nerve Plexus) lies between circular and longitudal mucle laters of muscularis externa
- Myenteric = Intestinal Muscle
- Entrict Neuerons control GI tract mobility
- Short Reflex arcs) Respond to stimuli inside GI tract
- controls segmentation and peristalsis
- involves pacemaker cells
- “Gut Brain” ) local intresnsic nerve plexus
- Long Reflex Arcs) Responds to stimuli inside or outside the GI tract
- Involve CNS centers and autnomic nerves
11
Q
Concepts of Regulating Digestive Activity
A
- Provoked by a range of mechanical and chemical stimuli
- Receptors are in wall of GI tract organs
- Reponds to stretch, changes in osmolality and ph, presense of substrate and end products of digestion
- Effectors of Digestive activity are smooth muscle and glands
- Initate reflexes
- Activate/ inhibit digestive glands
- stimulate smooth muscle to mix and move lumen contents
- Nuerons. (intrinsic and extrinsic) and hormones control activity
- Nuerons) control digestive system intresnsicly and extrensically
- Hormones) from cells in stomach/ small intestine stimulare tatget cells or organs
12
Q
Mouth
A
- Oral (buccal) cavity
- bounded by lips, cheeks, palate and tounge
- Lined with statified squamous epithelium
- Lips and Cheeks
- Contain obicularic oris and buccinator muscles
- Vestible (“Porch”) space betwen gums and lip
- Oral cavity proper) area within teeth and gums
- Labial Frenulum) median attachment of each lip to the gum
13
Q
Palate
A
- Hard Palate) Palatine bones and palatine process of maxillae
- forms a ridgid surface which the tounge forces food agaisnt while chewing
- Raphe) midlle rigdge which is slightly corrugated
- Soft Palate) fold formed mostly of skeletal muscle
- closes nasopharynx when swallowing
- Uvula projects downward from its free edge
14
Q
Tounge
A
- Skeletal Mucslce; Functions Include
- Repositioning/ mixing food during chewing
- Formation of bolus
- Initation of swallowing, speech and taste
- Intresnic Muscles) change shape of tounge as needed
- Extrensic muscles) change tounges position
- Lingual frenulum) attachemnt to the floor
- Papillae) holds tate buds
- Filifrom) whitish, give tounge rougness and provide friction
- Fungiform) reddish, scattered over tounge, contain taste buds
- Circumvallate (vallate) v shaped row on back of tounge; contains buds
- Folitate) on lateral aspects of the tounge
15
Q
Salivary Glands
A
- Extrinsic Salivary Glands) PRiduce saliva; lie outside oral cavity
- Partoid, Sumbandibular, Sublingual
- Minor/ Intresnsic Salivary glands) scattered throuought oral cavuty
- Buccal glands and others
- Function of Saliva
- cleans mouth, dissolves food chemicals for tatste, moistens food, and begins to break down starch via enzyme amylase
- Partoid Gland) major salivary glands
- anterior to ear; ecternal to masseter mucle
- Duct opens itno vestible next to second upper molar
- Submandibular
- Medial to body of mandible
- Duct opens at base of lungual frenulum
- Sublingual Gland
- Anterior to submandibular gland under tounge
- Opens via 10-20 ducts into floor of the mouts
- Two typed of silvary gland cell secretions
- Serous cells) watery, enxymes, ions, bit of mucin
- Mucous cells) mucus
- 97-99.5 percent water, slightly acidic
- 1500 ml/day
16
Q
Teeth
A
- Tear and grind food for digestion
- fully formed by age 21
- 20 Decidous teeth (decid = falling off)
- baby teeth
- Roots reabsorb when teeth fall out
- 32 Permanent Teeth
- All but third molars in by end of adolescense
- third molars ( widsom teeth) may or may not erupt
- Incisors) chisel shaped for cutting
- Canines) fang like teeth that tear or pierce
- Premolars (bicuspids) Broad corwn, Rounded cusps- grind/grush
- Molars) Broad corwn, Rounded cusps - best grinders
17
Q
Tooth Structure
A
- Crown) exposed part above gingiva (gum)
- covered by enamal (hardest substance in body)
- Enamal-producing cells degenrate when tooth erupts
- Root) Portion embed in jawbone
- Cement) calcified connective tissue
- Peridontal Ligament) Anchors tooth in bony socket
- Gomphosis) tooth joint
- Ginvival sulcus) groove where gums boarders tooth
- Dentin) bonelike material under enamal
- Pulp cavity) surrounded by dentin, Contains pult
- Root canal) where pulp cavity extends to root
- Apical Foramen) at proximal end of the root
18
Q
Tooth and Gum Disease
A
- Dental Caries (rottenness)(cavities) demineralization of enamal and entin from bacterial action
- dental plaque) adheres to teeth
- acid from bacteria dissolvles calcium salts
- Enzymes from bacteria digest organic matter
- Gingivits) plaque calcifies to from calculus (tarter)
- Calculus dirupts seal between gingicae and teeth
- Anerobic bacteria infects gums
- Peridontitis or Periodontal Disease (neglected gingivitis)
- Immune cells destroy peridontal ligament and dissolve bone
- Possible tooth loss
19
Q
Digestive Processes) Mouth
A
- Ingestion (eating)
- Mechanical Digestion (Mastication) (chewing)
- Cheeks and closed lips hold food between teeth
- Tounge mixes food with saliva; compacts food into bolus
- teeth cut and grind
- Propulsion (Deglutition or swallowing)
- Chemical digestion) salivary amulase and lingual lipase
- some drugs can be absorbed into mouth
20
Q
Pharynx
A
- Food passes from mouth > oropharynx > laryngopharynx
- Allows passage of food and air
- Statified squamous eitheliam
- Pharyngeal Constrictors) encircle the wall
21
Q
Esophagus
A
- Flat muscular tube from laryngopharynx to stomach
- Pierces diaphragm at esophageal hiatus
- Joins stomach at cardial oriface
- Gastrophageal (cardiac) sphincter) surrounds cardial orifice
- Esophegial mucosa
- Contains stratified squamous epithelium
- changes to simple columar at the stomach
- Esophageal glands in submucosa) secrete mucus to aid in bolus movment
- Adventiti is CT
22
Q
Deglutition (swallowing)
A
- Involves tounge, soft palate, pharynx, and esophagus
- 22 muscle groups help with swallowing
- Buccal Phase
- Occurs in mouth, is voluntary ends when food leaves the mouth
- Pharyngeal-esophageal pase
- Involuntary- primarrly vagus nerervr
- Controlled by swalllowing center in the medulla and pons
- Once food enters the pharynxm respiration momnetarily inhibited
- Solid food passes from oropgaynx to the stomach.
