Upper GIT Flashcards
What are the 6 stages of digestion?
- Ingestion
- Secretion
- Mixing and propulsion
- Digestion
- Absorption
- Defecation
How can the abdominal cavity be split?
4 quadrants
9 regions
What is the peritoneum?
Peritoneum is a thin, serous membrane that lines the abdominal and pelvic cavities
2 continuous layers
Parietal - lines abdominal cavity
Visceral - covers abdominal viscera
What does intraperitoneal mean?
Completely covered by peritoneum
What does retroperitoneal mean?
incompletely covered by peritoneum.
What is a mesentry?
Abdominal organs attach to each other and the wall via double folds of peritoneum called mesenteries
Act as a conduit for blood vessels and nerves to target organs, which allows them to absorb nutrients which have been released in the digestive process
What are the 6 layers of the anterior abdominal wall?
Skin
Subcutaneous fat
Muscle
Deep fascia
Extraperitoneal fat
Parietal peritoneum
Starting superficial to deep, what are the muscles of the anterior abdominal wall?
External oblique»_space; internal oblique»_space; Transverse abdominis»_space; Rectus abdominins
What are the 4 tissue layers that compose the GIT?
Mucosa
Submucosa
Muscularis
Serosa/adventitia
Role of mucosa.
Mucus membrane.
Portion called lamina propria which contains blood vessels and lymphatics.
Thins muscularis mucosae which causes secretion of substances from epithelial cells into lumen of GIT.
Role of submucosa.
Broad layer of dense connective tissue. Blood and lymphatic vessels located here. Conduit for network of nerve.
Role of Muscularis Propria.
Double layer of smooth muscle
Inner circular layer
Outer longitudinal
Contraction of these layers promotes mechanical digestion and GI motility
Controlled by another network of nerves called myenteric plexus
Role of Serosa / adventitia .
Layer of peritoneum and an overlying layer of loose connective tissue
GIT in abdominal cavity has serosa.
Mouth, pharynx and oesophagus have adventitia which is a dense sheath of collagen fibres.
Describe the features of the teeth.
Teeth - hard heavily mineralised structures that are embedded in the maxilla (upper bone) and mandible (jaw bone). Involved in mastication, the 1st stage of digestion.
Describe the features of the gingivae.
Gingivae (gums) - specialised regions of oral mucosa, surround teeth and help anchor the teeth into maxilla/mandible.
Describe the features of the tongue.
Tongue - important muscular organ, very mobile, many functions; eg, help with swallowing, contains taste buds, has lymphoid tissue to combat pathogens.
Describe the features of the palate.
Palate - roof of the mouth. Anteriorly is hard palate as maxilla bone just above, posteriorly is soft palette contains uvula which separates the region from the posterior nasal cavity.
Describe the features of the arches of the mouth.
Arches of the mouth - anterior arch called the palatoglossus (pala - palate, glossus - tongue). Posterior arch is called palatopharyngeus. These arches are the division between the mouth and the pharynx.
Function and morphology of canines.
Function as holding or grasping teeth
Protect the jaw joint during side jaw movements
Longest teeth and normally most stable due to root length
4 in total
Function and morphology of incisors.
Designed to cut
8 in total
Function and morphology of premolars.
Cross between canines and molars
2/3 cusps do sometimes referred to as bicuspids
Hold food but mainly help grind food.
Function and morphology of molars.
Most posteriorly placed teeth
4 cusps - resembles 2 premolars fused
Chew and grind up food
12 in total; 3 in each quadrant
What is the role of saliva?
Lubricates food, forming a bolus which can then easily be pushed down the GI tract.
Also acts as an intrinsic mouthwash as it has antimicrobial properties
Keeps the mucosa of oral cavity moist - essential for speech and protecting the oral cavity against the mechanical damage of fragmentation by teeth.
What are the 3 major paired salivary glands.
Parotid
Submandibular
Sublingual
Detail on parotid gland.
Parotid gland is a serous only gland. 1 duct. Facial nerves runs through parotid gland, splitting it into superficial and deep portions.
Detail on submandibular gland.
Submandibular gland has both serous and mucus secretions. 1 duct. It has deep and superficial portions.
Detail on the sublingual gland.
Sublingual gland has 8-12 short ducts. Mucus only gland.
What are the 2 functions of the pharynx?
- conducting air into larynx, trachea and lungs
- Directing food into the oesophagus
What are the 3 functional parts of the pharynx?
nasopharynx
oropharynx
laryngopharynx
Role of nasopharynx
Respiratory function
Superior to soft palette
Posterior extension of nasal cavity
Role of oropharynx
Mainly digestive function
Involved in swallowing
Transfers food from mouth through the pharynx and oesophagus to the stomach
Role of larynx and laryngopharynx.
Larynx is superior portion of the respiratory tracts
Laryngeopharynx lies posterior to the larynx
Larynopharynx eventually narrows to become continuous with the oesophagus
Explain the role and parts of the oesophagus.
Muscular tube
Transmits food from the pharynx to the stomach
Superior third is skeletal muscle (under voluntary control); inferior third is smooth muscle (involuntary control)
Composed of 3 parts:
Cervical (neck)
Thoracic
Abdominal (once passed through diaphragm)
What are the roles of oesophageal sphincters.
Both ends have a sphincter
Sphincters help prevent backflow
Upper oesophageal sphincter constricts to prevent the swallowing of air
Anatomical sphincter: striated muscle
Lower oesophageal sphincter prevents regurgitation of stomach contents
Physiological sphincter: other components that are not muscle, in this case angle of stomach and cura of diaphragm
Explain the role of the diaphragm.
Musculo-tendinous partition separating the thoracic and abdominal cavities
Chief muscle of inspiration
Diaphragm descends during inspiration and ascends during expiration
Increases abdominal pressure
Has apertures to allow structures to pass from the thoracic cavity to the abdominal cavity
Vena Cava (T8)
Oesophagus (T10)
Aorta (T12)
Acts as a physiological sphincter for lower oesophagus
What are the 4 parts of the stomach?
Cardia
Fundus
Body
Pylorus
What is omenta?
Double folds of peritoneum like mesentery
Greater omentum
Prevents visceral peritoneum from adhering to the parietal peritoneum
Forms adhesions adjacent to an inflamed organ
Minimise spread of intraperitoneal infections
Lesser omentum
Portal triad enclosed in free edge between liver and duodenum
What are the functions of the stomach?
- food blender
- acts as reservoir
- pylorus communicates with duodenum
What are the interior features of the stomach?
- rugae = longitudinal folds that allow the stomach to distend fully to increase the surface area.
- 3 muscles layers to aid mechanical digestion
What are the 3 stomach cells? What is their role?
Mucous cells
Mucous prevents abrasion of gastric mucosa
Parietal cells
Produce intrinsic factor (important for absorption of vitamin B12)
Produces 3L of acid (HCl) per day
Peptic chief cells
Produce inactive enzyme (pepsinogen) which is then activated by the acid into active form pepsin.
What is the role of the duodenum?
1st and smallest section of small intestine.
Pancreatic secretions and bile enter into descending portions via the major duodenal papilla
