Anatomy Flashcards
Name the components of the GI tract from head to perineum
- head; oral cavity, pharynx
- neck; pharynx, oesophagus
- chest; oesophagus
- abdomen; stomach small intestine, large intestine, most accessory organs of the GI tract
- pelvis; rectum, anal canal
- perineum; anus
What are the four main functions of the upper GI tract?
- mastication
- taste
- deglutition (swallowing)
- salivation
What structures are involved in mastication?
- temporomandibular joint
- muscles of TMJ, face and tongue
- dentition (teeth)
What structures are involved in taste?
- tongue
- salivation
- mastication
What structures are involved in deglutition?
- tongue
- palate
- pharynx
- oesophagus
What structures are involved in salivation?
- parotid gland
- submandibular gland
- sublingual gland
- minor glands
Describe mastication
- the process of chewing
- conducted by the movement of the jaw and tongue, to breakdown food
- mastication facilitates taste and digestion by mixing food with saliva
Name the four quadrants of teeth
- upper right
- upper left
- lower left
- lower right
What is the upper and lower dental arches referred to?
- upper = maxillary
- lower = mandibular
How many teeth do adults have?
32
Name the types of teeth and what number they refer to
- molars; 6,7,8
- premolars; 4 and 5
- canine; 3
- incisor; 1 and 2
- wisdom tooth; 8
Where does the opening and closing of the jaw occur?
TMJ, temporomandibular joints
The 4 muscles of mastication are supplied by which nerve?
- CN V3
- mandibular division of trigeminal nerve
What is the masseter muscle?
Angle of mandible to zygomatic arch
What is the temporalis m?
Coronoid process of mandible to temporal fossa
What is the later pterygoid?
- muscle
- condyle of mandible to pterygoid plates of sphenoid bone
What is the medial pterygoid?
- muscle
- angle of mandible (medial side) to pterygoid plates of sphenoid bone
The mandibular division of trigeminal nerve (CNV3) provides what types of fibres?
- sensory
- motor
Describe the course of the mandibular division of trigeminal nerve (CNV3)
- from pons
- through foramen ovale
- to muscles of mastication and sensory area
What are the four types of papillae?
- foliate papillae
- vallate papillae
- fungiform papillae (singular papilla)
All with taste buds - filiform papillae (touch, temperature etc)
Describe the course of the facial nerve
- from pontomedullary junction
- travel through temporal bone via internal acoustic meatus then stylomastoid foramen
The facial nerve supplies what with which fibres?
- supply taste to the anterior 2/3 of the tongue
- muscles of facial expression
- glands in floor of mouth
- special sensory, sensory, motor and parasympathetic
Describe the sensation supply of the superior half of the oral cavity
- gingiva of oral cavity and palate
- general sensation CN V2
Describe the sensation supply of the inferior half of the oral cavity
- gingiva of oral cavity and floor of mouth
- general sensation CNV3
Describe the gag reflex
- a protective reflex that prevents foreign bodies from entering the pharynx or larynx
- the sensory part of this reflex is carried by nerve fibres within CN IX
- the motor part is carried by nerve fibres within CN IX and CN X
- part of the reflex response to touching the posterior wall of the oropharynx is to constrict the pharynx, as the patient attempts to dose it off as an entry point into the body
What is the purpose of spraying a local anaesthetic at the back of the throat?
Will block sensory action potentials in CNV2, CNV3, CN VII and CNIX
- numbs the area ready for the endoscope
Describe the course of CNV2
- maxillary division of trigeminal nerve (CNV2), sensory fibres
- course; from pons, through foramen rotundum, to sensory area (mid-face)
Describe the course of the glossopharyngeal nerve (CN IX)
- from medulla
- through jugular foramen
- to posterior wall of oropharynx (sensory), parotid gland (secretomotor) and post 1/3rd tongue (sensation and taste)
Describe the surface anatomy of the parotid gland
- parotid duct crosses face, secretes into mouth by upper 2nd molar
Describe the surface anatomy of the submandibular gland
- submandibular duct enters floor of mouth and secretes via lingual caruncle
Describe the surface anatomy of the sublingual gland
- lays in floor of mouth, secretes via several ducts superiorly
What are the three pairs of salivary glands and which nerve supplies them?
- parotid; CNIX
- submandibular; CNVII
- sublingual; CNVII
Describe the extrinsic muscles of the tongue
Function to change the position of the tongue during mastication, swallowing and speech
Describe the intrinsic muscles of the tongue
- 4 pairs of skeletal intrinsic muscles
- located dorsally / posteriorly
- modify the shape of the tongue during function
All tongue muscles are innervated by which nerve?
The hypoglossal nerve (CNX11)
EXCEPT PALATOGLOSSUS
Describe the course of the hypoglossal nerve (CNXII)
- from medulla
- through hypoglossal canal
- to extrinsic and intrinsic muscles of the tongue (except palatoglossus)
Describe the posterior view of the pharynx
- 2 circular constrictor muscles
- voluntary muscle
- external circular layer overlap each other and contract sequentially
- innervated by CN X (vagus)
- all insert onto the midline raphe
- both layers elevate pharynx and larynx, attach to larynx, contract to shorten pharynx, raise the larynx to close over the laryngeal inlet
Describe the anatomy of swallowing
- close the lips to prevent drooling (orbicularis oris and cranial nerve VII)
- the tongue (cranial nerve XII) pushes the bolus posteriorly towards the oropharynx
- sequentially contract the pharyngeal constrictor muscles (cranial nerve X) to push the bolus inferiorly towards the oesophagus
- at the same time he inner longitudinal layer of pharyngeal muscles (cranial nerves IX and X) contracts to raise the larynx, shortening the pharynx and closing off the laryngeal inlet to help prevent aspiration
5. the bolus reaches the oesophagus
Describe the enteric nervous system
- extensive network of nerves, found only in walls of GI tract
- acts independently of other parts of nervous system, but can also be influences by autonomic motor nerves
- parasympathetics (speed up peristalsis)
- sympathetics (slow down peristalsis)
Where does the oesophagus begin?
Begins at the inferior edge of circopharyngeus muscle (vertebral level 6)
Describe the oesophagus
- inferior continuation of laryngopharynx
- is a muscular tube, walls sit together when there is no food present
- has an anatomical upper sphincter and a physiological lower oesophageal sphincter
- aid in controlling movement
Describe the oesophageal plexus
- runs on surface to supply smooth muscle within its walls (distally)
- contains parasympathetic nerve fibres (vagal trunks) and sympathetic nerve fibres
- these fibres influence the enteric nervous system to speed up (P) or slow down (S) peristalsis
Where does the oesophagus terminate?
Terminates by entering the cardia of the stomach
Describe the position of the oesophagus in the root of the neck
- posterior to trachea
- anterior to vertebral bodies
Describe the position of the oesophagus in the chest
- posterior to the heart
- in contact with the left atrium
Describe the position of the oesophagus in the abdomen
- through diaphragm at T10 vertebral level
- immediately connects with stomach
Describe the cervical constriction of oesophageal positioning
- circopharyngeus muscle
Describe the thoracic constrictions of oesophageal positioning
- arch of aorta
- left main bronchus
Describe the diaphragmatic constriction of oesophageal positioning
- result of passing through diaphragm
- lower oesophageal sphincter
Describe the lower oesophageal sphincter
- physiological rather than anatomical sphincter
- helps reduce the occurrence of reflex
- presence of a hiatus hernia will reduce its effectiveness can lead to reflux
- lies immediately superior to gastro-oesophageal junction
- abrupt change in type of mucosa lining the wall - zline
Name factors that produce the sphincter effect
- contraction of diaphragm
- intrabdominal pressure slightly higher than intragastric pressure
- oblique angle at which oesophagus enters the cardia of stomach
Describe the anatomical position of the stomach
- lies mainly in the left hypochondrium, epigastric and umbilical regions when the patient is supine
What is the fundus?
The superior part of the stomach
Describe the arterial supply to the abdominal organs
- three midline branches of the abdominal aorta
- coeliac trunk (foregut organs)
- superior mesenteric artery (midgut organs)
- inferior mesenteric artery (hind gut organs)
Describe the formation of the vitelline duct
- initially the midgut is completely open into the yolk sac
- as folding continues it narrows for a connecting, vitelline duct
- it becomes incorporated into the umbilical cord
Describe the formation of the oesophagus
- respiratory diverticulum appears end of week 3
- weeks 4-7 oesophagus lengthens rapidly due to descent of heart and lungs
- failure of oesophagus to grow in proportion with neck and thorax can lead to a short oesophagus
- resulting in stomach being placed cranially in the thorax forming a congenital hiatal hernia
Describe the formation of the stomach
- stomach starts as a fusiform dilation
- dorsal wall undergoes rapid growth to form the greater curvature
- ventral wall growth is slower resulting in the lesser curvature
Describe the rotation of the stomach
- clockwise 90 degrees around the longitudinal axis (LARP, left anterior, right posterior)
- anteroposterior axis rotation brings pyloris upwards and fundus downwards
Describe the primitive dorsal and ventral mesenteries
- mesenteries are a continuous layer of serous membrane
- they attach the gut tube to the anterior (ventral) and posterior (dorsal) walls of the abdomen
Describe the formation of the omental bursa
- omental bursa (AKA lesser peritoneal sac) is the (peritoneal) space posterior to the stomach
- rapid growth of dorsal mesentery and stomach rotation around the longitudinal axis
- the rest of the space in the peritoneal cavity is known as the greater sac
- epiploic foramen (of winslow) connects the two (greater and lesser sacs)
Describe the foramen of the greater omentum
- dorsal mesentery continues to develop as a double layered sac over the small intestine and transverse colon
- these layers fuse to extend from the greater curvature of the stomach
- forming the greater omentum (apron like structure)
Describe the formation of the duodenum
- both foregut and midgut structure
- as stomach rotates the duodenum move from the midline to the right side of the abdominal cavity
- dorsal mesentery fuses with peritoneum covering the posterior abdominal wall
- duodenum (parts 2 and 3) and pancreas become retroperitoneal
Describe the development of the midgut
- in week 5, mid gut rapidly expands forming the primary intestinal loop
- cranial (cephalic) limb, distal duodenum, jejunum and upper ileum
- caudal limb - lower ileum, cecum, ascending colon and proximal 2/3rds of transverse colon
Describe physiological herniation of the midgut
- in week 6, rapid growth and expansion of the liver causes physiological herniation of midgut
- the cranial (cephalic) limb continues to lengthen
- intestinal loops move through umbilical cord to lie outside the developing embryo
Describe rotation of the midgut
- as lengthening continues, the midgut rotates 90 degrees clockwise (patients perspective) and herniates through umbilical cord
- small intestine and large intestine growth continues to form coils (large intestine does coil)
- during week 10, intestines retract back into abdomen with a further 180 degree clockwise turn (270 degrees total)
- jejunum first then cecal bud
- cecal bud then descends from right lobe of liver to right iliac fossa
Describe fixation of intestines
- the dorsal mesentery of the gut is still present and connects to the posterior abdominal wall
- connected around the axis of the superior mesenteric artery
- the ascending and descending colon mesentery fuse with peritoneum to place them in retroperitoneal space
What is omphalocele?
- failure of intestinal loop to return into abdomen
- presents as shiny sac at the base of umbilical cord
- 2.5/10,000 births
- high mortality rate
- often associated with cardiac and neural tube defects
What is gastrochisis?
- protrusion of abdominal content through wall lateral to umbilical cord
- due to abnormal closure around the connecting stalk
- 1 in 10,000 births
Describe the development of the hindgut
- terminal end of hindgut is an endodermal lined pouch called the cloaca
- in contact with surface ectoderm of proctodeum to form the cloacal membrane
- urorectal septum partitions the cloaca into; upper rectum . anal canal and urogenital sinus
- urorectal septum fuses with the cloacal membrane at the future site of the perineal body
Describe the formation of the liver and biliary system
- a ventral overgrowth of foregut end weeks 3 into ventral mesentery
- outgrowth termed hepatic diverticulum (liver bud) that penetrate septum transversum
- cranial portion = liver
- caudal portion = bile duct
Outgrowth from the bile duct gives rise to what?
The gallbladder and cystic duct
Describe the formation of the liver
- hepatic cords form, which intermingle with the umbilical and vitelline veins to give hepatic sinusoids
- vitelline veins carry poorly oxygenated but nutrient rich blood to the developing embryo
- endoderm; liver cells (parenchyma) and lining of biliary tree
- septum transversum; hematopoietic cells, Kupffer cells and connective tissue
Describe the formation of the spleen
- mesoderm derivative (not gut tube)
- develops in 5th week
- initially haematopoetic
- develops into lymphatic organ during weeks 15-18
- lobular appearance but lobes normally regress before birth, notches in adults
Describe the small intestine
- around 7m long and from proximal to distal is made up of;
- duodenum (short)
- jejunum (3m)
- ileum (4m)
Describe the large intestine
- from proximal to distal is made up from;
- colon; caecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon)
- rectum
- anal canal
- anus
Nam the abdominal organs
- liver
- oesophagus
- stomach
- gall bladder
- pancreas
- large intestine
- small intestine
- rectum
- anal canal
- anus
- spleen
- kidneys
- adrenal glands
Name the abdominal organs of the foregut
- oesophagus to mid-duodenum
- liver and gall bladder
- spleen
- 1/2 of pancreas
Name the abdominal organs of the midgut
- mid-duodenum to proximal 2/3rds of transverse colon
- 1/2 of pancreas
Name the abdominal organs of the hindgut
- distal 1/3 of transverse colon to proximal 1/2 of anal canal
What are the nine regions of abdominal organs?
- right hypochondrium
- epigastric
- left hypochondrium
- right lumbar
- umbilical
- left lumbar
- right inguinal
- pubic
- left inguinal
What is the peritoneum?
- a thin, transparent, semi-permeable serous membrane
- it lines the walls of the abdominopelvic cavities and organs
What lies between the visceral and parietal layers of peritoneum?
The peritoneal cavity, contains a small amount of lubricating fluid
What is peritonitis?
- blood, pus, faeces in the peritoneal cavity
- causes severe and painful inflammation of the peritoneum
How are organs classes depending on their relationship with the peritoneum?
- intraperitoneal
- retroperitoneal
- with a mesentery
Describe the intraperitoneal organs
- almost completely covered in visceral peritoneum
- minimally mobile
Describe the organs with a mesentery (intraperitoneal)
- covered in visceral peritoneum
- visceral peritoneum wraps behind the organ to form a double layer - mesentery
- mesentery suspends the organ from the posterior abdominal wall - very mobile
Describe the retroperitoneal organs
- only has visceral peritoneum on its anterior surface
- located in the retroperitoneum
What are the three type s of peritoneal formation?
- mesentery; usually connects organ to posterior body wall
- omentum (greater and lesser); double layer of peritoneum that passes from stomach to adjacent organs
- peritoneal ligaments; double layer of peritoneum that connects organs to one another or body wall
Describe the mesentery peritoneal formation
- have a core of connective tissue with blood and lymph vessels, nerve, lymph nodes and fat
- the mesentery proper of small intestine
- transverse and sigmoid mesocolon
- mesoappendix
- mesentery provide high level mobility