WEEK 1 Flashcards
What are the 5 functions of the oral cavity?
- Take in food and fluid, and hold it there
- Add saliva to wet and start digestion
- Taste
- Chew and swallow
- Protection (tonsils)
What is the difference between the oral cavity proper and the oral vestibule?
The oral cavity proper lies between the teeth ad the oral vestibule lies outside the teeth.
What structures form the boundaries of the oral cavity?
Anteriorly it extends from the upper and lower lips
Posteriorly to the palatoglossal arches or the anterior pillars of the fauces
Laterally it is bound by the cheeks
What 2 things is the hard palate made up of?
Maxilla
Horizontal plate of palatine bone
What 2 things does the ramus divide into?
Condylar and coronoid processes
What is the function of the following structures (i) retromolar fossa (ii) mandibular foramen (iii) submandibular fossa (iv) mylohyoid line (v) sublingual fossa?
(i) attachment of the lower end of the pterygomandibular raphe, between buccinator and superior constrictor
(ii) for the inferior alveolar or dental nerve to lower teeth
(iii) submandibular gland
(iv) attachment of mylohyoid muscle (floor of mouth)
(v) sublingual gland
How is the TMJ divided?
into 2 cavities by a disc
What movements does the TMJ make and what functions does this allow?
Protrusion, with depression along with retraction and elevation
Allow to open and close the mouth for chewing biting grinding and speaking
What is the function of the lateral pterygoid muscle?
Draws the disc and condyle forwards and downwards
It is the only primary muscle of mastication which opens the mouth
(gravity and digastric also help to open the mouth)
What is the 3 muscles which close the mouth?
- Medial pterygoid - elevates the mandible to close the mouth
- Temporalis
- Masseter
These 3 muscles are powerful elevators of mandible for biting, chewing and grinding
What structures make up the cheeks and lips (HINT: there’s 4)
- Muscles of facial expression
- Buccinator
- Orbicularis oris
- Lip and angle elevators and depressors
What is the functions of the cheeks and lips?
Keep food in mouth and between teeth
Speech formation
What type of epithelium lines the mucous membrane internally?
Non-keratinised, stratified squamous epithelium
Describe the buccinator muscle?
The cheek muscle
- compresses the vestibule and contributes hugely to orbicularis oris
What is the name of the point of crossover of the upper and lower buccinator fibres?
Modiolus
It is found just lateral to the angle of the mouth
How is there continuity between the oral cavity and pharynx?
Buccinator attaches to the maxilla and mandible
But also fuses with the superior pharyngeal constrictor at the pterygomandibular raphe
What is the upper attachment of the pterygomandibular raphe?
To the pterygoid hamulus - at the lower end of the medial pterygoid plate
What provides sensation to the skin of the cheeks and lips, plus the corresponding internal mucous membrane?
Branches from the maxillary and mandibular divisions of the trigeminal nerve (cranial V) V2 and V3
What structures make up the floor of the mouth?
What is the function of the floor of the mouth?
Muscular diaphragm of mainly mylohyoid suspended between the mandible and hyoid bone
It forms a mobile support for the tongue
What is the function of the tongue?
A bag of muscle for manipulating food and forming speech
What is the function of the (i) extrinsic (ii) intrinsic muscles of the tongue?
(i) alter positon
(ii) alter shape
What are the muscles relating to the tongue? What is their nervous supply?
Genioglossus plus intrinsic muscles
And other extrinsic - palatoglossus, hyoglossus, styloglossus
Supplied by the Hypoglossal nerve (XII) except palatoglossus which is supplied by the vagus nerve (X)
What is the function of (i) genioglossus (ii) palatoglossus and styloglossus (iii) hypoglossus?
(i) protrudes tongue
(ii) draws tongue upwards and backwards
(iii) draws the sides downwards
What is the external appearance of the tongue?
ensure to mention papillae
Terminal sulcus divides it into an anterior 2/3 and a posterior 1/3 (or pharyngeal part)
Its surface is covered by different types of papillae which make it ‘furry’ to grip food - and also possible housing taste buds
What is the function of the tongue?
Food is taken into oral cavity, lies between the teeth (by lips, cheeks and tongue) for mastication
Saliva added to start digestion and to lubricate bolus
Tongue forms bolus and pushes it backwards to be swallowed
The tongue is also for taste and speech formation
What is the motor and sensory supply of the tongue?
MOTOR = hypoglossal(XII) to all except palatoglossus which is vagus (X)
SENSORY = Anterior 2/3 via lingual (V3) for general sensation and taste
Posterior 1/3 via glossopharymgeal (IX) for both general sensation and taste
What is the blood supply of the tongue? Where do these vessels originate from/drain into?
Lingual artery from external carotid
Deep and dorsal lingual veins which converge on the internal jugular
What is the lymphatic supply of the tongue?
Posterior 1/3 is to the superior deep cervical nodes
Middle 1/3 is to inferior deep cervical nodes medially (this is where the crossing over occurs) and to the submandibular nodes laterally
The Anterior 1/3 is to the submental lymph nodes
What are the 3 functions of the salivary glands?
- Commence digestion
- Lubricate food
- Maintain health of the teeth and gums
What are the 3 types of salivary glands?
Parotid (serous)
Submandibular (mucous and serous)
Sublingual (mucous)
What is the nervous supply of the glands?
Parasympathetic, secretomotor supply from glossopharyngeal nerve (IX) and facial nerve (VII)
What do the sublingual glands form?
Sublingual folds under the mucous membrane - they open by separate ducts into the floor of the mouth
What ducts can be obstructed by stones? Describe said ducts.
Submandibular ducts
- lie beside submandibular glands, but they open at the papillae, either side of the frenulum
Describe the anatomy of the submandibular gland.
Has a superficial part outside mylohyoid, but turns around the posterior edge of the muscle to become deep
The duct passes anteriorly alongside the SLG to reach the papilla
What is the location of the lingual nerve in relation to the submandibular ducts?
Wind from lateral to inferior to medial to the duct
What is the location of the parotid gland?
in the investing layer of fascia between mandibular ramus and sternocleidomastoid, inferior to the auricle, and deeply as far as the styloid process
It overlaps masseter and sends a duct obliquely through buccinator into the oral cavity opposite the 2nd upper molar
What 3 things does the parotid gland contain?
- facial nerve (VII)
- retromandibular vein
- external carotid artery
What is the function of the (i) hard palate (ii) soft palate?
(i) assisting bolus formation and separation from nasal cavity
(ii) hangs like a curtain at back of mouth to stop food falling into pharynx and larynx. Tenses and elevates to separate naso from oropharynx during swallowing
What is most of the soft palate made of?
The aponeurosis of tensor palati, covered by mucous membrane
What is the function of the palatoglossal arches?
Separate the oral cavity from the oral pharynx
Where do the tonsils lie?
Behind the palatoglossal arches but in front of the pharyngeal arches
What is the anatomical position of Tensor palati?
Attaches to fossa above medial pterygoid plate and to cartilage of auditory tube
Lies outside the medial pterygoid plate and outside the pharynx
Until it becomes tendinous and curves around the pterygoid hamulus and flares into the soft palate as the palatine aponeurosis
What is the anatomical position of levator palati?
Arises from the apex of the petrous temporal bone and from the cartilage of the auditory tube
Lies inside the pharynx and inserts into upper aspect of palatine aponeurosis
What 2 things are attached to the auditory tube? What does swallowing do to said tube?
The tensor and levator palati
Swallowing opens the tube
What nerve supplies the tonsils? As a result where can pain be referred to?
Glossopharyngeal nerve (IX) referred pain to middle ear
What occurs whilst chewing food?
Oropharyngeal isthmus must be closed
- palatoglossus and palatopharyngeus contract to draw the palate down and the tongue slightly upwards, as well as drawing the palatoglossal and pharyngeal arches downwards and medially
What occurs during swallowing?
Tensor palati makes the aponeurosis tense so the levator palati can lift it to close the nasopharyngeal isthmus
Adult teeth are described in 4 quarters, what is contained within each quarter? How many teeth does a full set of adult teeth contain?
Molars - 3 Premolars - 2 Canine - 1 Incisors - 2 Total od 32 teeth
What are the molar roots related to?
The inferior alveolar nerve in the mandibular canal
What is the nervous supply of the (i) upper (ii) lower teeth?
(i) alveolar branches of maxillary nerve (V2)
(ii) Inferior alveolar branch of V3
What is the function of the (i) nasopharynx (ii) oropharynx?
(i) transports air and is divided from the oropharynx by the soft palate
(ii) transports air plus food and fluid - these must be separated so air to larynx and food and fluid continues into the laryngopharynx
The folds raised by which 3 longitudinal muscles elevate the pharynx and larynx?
Palatoglossus
Palatopharyngeus
Salpingopharyngeus
Where is there a risk of foreign bodies getting stuck in the pharynx?
Piriform fossa
What is the location of the piriform fossa?
Between the quadrangular membrane of the larynx and the side wall of the pharynx
What is the function of the pharyngobasilar fascia? Where is it located?
Holds the nasopharynx open
Found superiorly to the superior constrictor
What are the names of the 3 constrictors? What is their function?
Superior, middle and inferior
Function is to squeeze bolus towards the oesophagus
What is the function of the elevators of the pharynx?
The lift the pharynx to receive bolus
What are the 4 skeletal attachments of the pharynx?
- Medial pterygoid plate of sphenoid
- Pharyngobasilar fascia attaches to the cartilage of the auditory tube so that the tube opens into the upper nasopharynx
- Levator palati arises from the apex of the petrous temporal bone, inside the pharyngeal attachment
- Fascia, and the posterior, midline pharyngeal raphe formed by the constrictors attaches to the pharyngeal tubercle
What are the 3 parts of the hyoid bone?
Body
Greater horn
Lesser horn
What is the attachment and function of the stylohyoid ligament?
Attaches to the lesser horn of the hyoid to suspend it from the styloid process of the skull
With regards to the TMJ, how is the mouth opened?
Protrusion and depression
the condyle and disc glide together
What is the significance of infection spreading from the fascial planes?
Could track backwards and possibly cause laryngeal oedema (therefore airway obstruction)
The roots of the upper teeth can extend into what?
Into the sinus - the removal may cause a fistula
What is the attachment of (i) Pharyngobasilar fascia (ii) Superior constrictor (iii) Middle constrictor (iv) Inferior constrictor?
(i) the medial pterygoid plate (posterior nasal conchae)
(ii) continues to form the pterygo-mandibular raphe with buccinator
(iii) Hyoid bone and stylohyoid ligament
(iv) oblique line of the thyroid cartilage (thyropharyngeus), cricoid cartilage (cricopharyngeus) and to the fascia on cricothyroid
What does the free lower edge of the pharyngobasilar fascia contribute to?
To the pharyngeal sphincter which separates naso from oropharynx during swallowing
What pierces the thyro-hyoid membrane?
Internal laryngeal nerve and vessels
What is the route of the (i) external laryngeal nerve (ii) recurrent laryngeal nerve?
(i) cricothyroid
(ii) passes deep to inferior constrictor to reach the larynx
What sensation does the internal laryngeal nerve give?
Sensation to larynx ABOVE the vocal folds
When the 3 pharyngeal constrictors contract sequentially what movement do they provide?
They force a food bolus downwards to the oesophagus
What is the innervation of all 3 pharyngeal constrictors?
By the pharyngeal branch of the vagus nerve (X)
Where does the buccopharyngeal fascia lie?
Externally all around the muscular pharynx and blends with the pretracheal fascia
What is the cricopharyngeus? What is its function?
The lower circular part of the inferior constrictor that forms a sphincter around the upper oesophagus to prevent air being drawn into the stomach during inhalation
What is the palatopharyngeal sphincter (Passavant’s muscle/ridge)?
It coincides with the inferior edge of the pharyngobasilar fascia
It is essentially a muscular ring derived from either the superior constrictor of palatopharyngeus
It provides a socket into which the soft palate can move when it is tensed and elevated in swallowing
Pharyngobasilar fascia and constrictors overlap so that there are usually 3 layers. Name these 3 layers.
- Pharyngobasilar fascia, superior and middle constrictor
- Sup, middle and inferior constrictor
- Middle and inferior constrictor
The point just above the cricopharyngeal sphincter is where the layer consists of only the middle and inferior constrictor, what complications can arise from this?
Potential weakness (dehiscence of Killian) - a pharyngeal diverticulum may occur (especially in cricopharyngeal uncoordination
What is the function of Palatopharyngeus, one of the pharyngeal elevators?
Elevates the pharynx and larynx
Draws the soft palate down
Brings the palatopharyngeal arch towards the midline to help separate the oral cavity from the pharynx
What is the location of stylopharyngeus? What is its innervation?
Descends from the styloid process to pass between the superior and middle constrictors and fan into the pharyngeal surface Glossopharyngeal nerve (IX)
What is the (i) location (ii) function and (iii) innervation of salpingopharyngeus?
(i) descends into the pharynx from the cartilage of the auditory tube
(ii) elevates pharynx and larynx. Also helps to open the auditory tube during swallowing for pressure equalisation in the middle ear
(iii) vagus (X) nerve
What are tonsils?
Clusters of lymphocytes around an invagination of overlying epithelium (i.e. crypt)
In what 3 places is tonsillar tissue found? What are the names given to the tonsils found at each of these places?
- Posterior 1/3 (pharyngeal) part of tongue - LINGUAL
- Roof of nasopharynx (adenoid) - PHARYNGEAL/ADENOID
- Opening of auditory tube - TUBAL
What can swelling of the pharyngeal or tubal tonsil cause?
May obstruct the airway and the auditory tube
- mouth breathing and middle ear infection
What is the vallecula?
A pit/fossa between the tongue and epiglottis
- waiting for foreign bodies
NOTE: there is one on each side
What complication can occur with a catheter intended for the auditory tube?
It may miss an enter the pharyngeal recess (behind the auditory tube)
If the pharynx is pierced, the catheter could enter the internal carotid artery
What is the arterial supply of the (i) upper pharynx (ii) lower pharynx?
(i) branches of the external carotid
(ii) branches of the inferior thyroid branch of thyrocervical from subclavian
What is the (i) venous drainage (ii) lymphatic drainage of the pharynx?
(i) it includes the pterygoid plexus but essentially converges on the facial and int. jugular veins
(ii) includes retropharyngeal, paratracheal and infrahyoid nodes but converges on deep cervical nodes
Where does the lymph from the palatine tonsil drain to?
To the jugulodigastric
If inflamed it is palpable
What is the sensory supply of the pharynx?
- Oropharynx, palatine tonsil, inf aspect of soft palate and post 1/3 tongue = glossopharyngeal (IX) - middle ear referred pain
- Laryngopharynx, vallecula and epiglottis - vagus (X)
What is the motor nerve supply of the pharynx?
Musculature = all by vagus except stylopharyngeus which is glossopharyngeal
Parasympathetic secretomotor = vagus (X) and facial (VII) nerves
What 2 nerves are involved in the gag reflex
Afferent = glossopharyngeal (IX) Efferent = vagus (X)
What are the 5 stages involved in swallowing?
- The bolus is pushed towards the back of the oral cavity by raising the tip and body of the tongue upwards towards the palate (through the use of mylohyoid and intrinsic tongue muscles)
- Styloglossus then pulls the tongue upwards and backwards to tip the bolus through the oropharyngeal isthmus and into the pharynx
- The soft palate is tensed and elevated to sit within Passavant’s ridge and separate naso from oropharynx. The 2 sets of arches relax and move laterally
- Pharynx and larynx have been elevated by the longitudinal muscles
- Relaxation of the elevators allows the pharynx and bolus to descend, while sequential contraction of contrictors pushes bolus towards the oesophagus
What movements ensure that food does not go into the larynx?
Larynx is drawn anteriorly by geniohyoid
As the tongue has been drawn posteriorly the larynx effectively lies tucked under the back of the tongue - forcing the epiglottis backwards like a lid over the already shut laryngeal inlet
What movements allow respiration to commence following swallowing?
Pharyngeal and laryngeal depression
- relaxation of the elevators
- elastic recoil
What are the 8 points you would ask in the HPC for gastrointestinal questions?
- Abdominal pain (socrates)
- Anorexia and weight change
- Dyspepsia/indigestion
- Dysphagia
- Nausea and vomiting
- GI tract bleeding
- Jaundice
- Change in bowel habit (constipation/diarrhoea)
What are the main 9 points you would ask in the HPC for genitourinary questions?
- Urinary frequency
- Dysuria - pain/burning when urinating
- Nocturia - passing urine at night
- Incontinence - stres or urge or mixed
- Hesitancy - want to but it wont start
- Urinary urgency - need to go NOW
- Urinary flow - strength of stream
- Haematuria - blood in urine
- Loin pain
What are other questions to consider in the HPC of GU?
Vaginal bleeding Vaginal discharge Menstrual history Obstetric history Sexually active? Contraception Last menstrual period (LMP)
Name, and describe the location of the 9 regions of the abdomen.
TOP (from R. to L) - R. hypochondrium - Epigastric - L. hypochondrium MIDDLE (R. to L) - R. lumbar (flank) - Umbilical - L. lumbar (flank) BOTTOM (R. to L) - R. iliac fossa - hypogastric (suprapubic) - L. iliac fossa
If pain radiates to the (i) back (ii) shoulder tip (iii) from the loin to the groin, what diseases could these suggest?
(i) pancreatitis
(ii) diaphragmatic irritation
(iii) renal colic
What questions should be asked with regards to anorexia and weight change?
‘Hows your appetite?’/ Has it changed?/ over how long?
- Do you still enjoy food/meals?
- Has your weight changed? Over how long?
- Have you been trying to lose weight?
- Are your clothes looser/tighter than normal?
- Still using the same notch on your belt?
What are the common causes of (i) weight gain (ii) weight loss?
(i) Fluid gain (cardiac failure, liver disease, nephrotic syndrome)
Hypothyroidism
Depression
Increased energy input/output ratio
(ii) Malignancy
Malabsorption (chronic pancreatitis, coeliacs, Crohn’s)
Metabolic diseases (diabetes, hyperthyroid, renal disease, chronic infection
Psychiatric causes (depression, dementia, anorexia nervosa)
Malnutrition etc.
What is dyspepsia? What usually triggers it and what usually relieves it?
Heartburn, acidity, pain, discomfort, nausea, wind, fullness or belching
Usually triggered by food
May be relieved by antacid “Gaviscon”
What is Dysphagia? What questions should be asked with regards to dysphagia?
A difficulty in swallowing
Qs: where do you feel it sticking? Itermittent/progressive?
Solids/Liquids?
Associated symptoms (heart burn, weight loss)
Complete obstruction and regurg of foodstuffs
What are the causes of (i) oral (ii) neurological (iii) neuromuscular (iv) mechanical dysphagia?
(i) painful mouth ulcers tonsilitis/pharyngitis/glandular fever (ii) CVA (stroke) Bulbar or pseudobulbar palsy (iii) achalasia Pharyngeal pouch Myasthenia gravis Diffuse oesophageal spasm (iv) Oesophageal carcinoma, peptic oesophagitis, benign structure, extrinsic compression
What is haematemesis? What are the causes?
Vomiting blood - either red or 'coffee-groung' CAUSES: - gastric or duodenal ulcer (50%) - gastric erosions (15-20%) - varices (10-20% - Mallory-Weiss syndrome (5-10%) - Reflux oesophagitis (2-5%) - Gastric carcinoma (uncommon)
What is the commonest cause of serious and life threatening GI bleeding?
Peptic ulceration
What is melaena? What is it most commonly caused by?
The passage of black tarry stools
Usually second to bleed in oesophagus/stomach/duodenum
Most commonly caused by chronic peptic ulceration
With regards to lower GI bleeding what (i) questions should be asked (ii) associated symptoms (iii) causes?
(i) duration and frequency? Is it mixed with stool? Associated symptoms?
(ii) diarrhoea, constipation, abdominal pain, change in bowel habit, retal/anal pain
(iii) Haemorrhoids/anal fissue/ diverticular disease/ large bowel polyps or carcinoma/IBD
What does painless jaundice suggest?
Carcinoma of the head of the pancreas
If a pt comes in with jaundice, what questions should you ask?
Duration Associated symptoms Colour of stool and urine Travel Shellfish consumption Blood transfusion Alcohol consumption Changes in medication IV drug use Unprotected sex
What are the common causes of (i) constipation (ii) diarrhoea?
(i) diet/dehydration, painful anal conditions (fissure), immobility, medication (opiates), hypothyroid, colonic/rectal carcinoma, neuromuscular (SC or parkinsons), hypercalcaemia, IBS
(ii) diet, stress, infection (gastroenteritis, food poisoning), inflammation (ulcerative colitis, Crohns), endocrine (hyperthyroid), malabsorption (coeliac, pancreatic disease), medication, IBS
What are the symptoms of a (i) lower UTI - cystitis (ii) upper UTI - pyelonephritis?
(i) dysuria, frequency, urgency, suprapubic discomfort, (haematuria)
(ii) loin pain, fevers, rigors, flank tenderness, urinary frequency, dysuria, (haematuria)
What are the 10 ‘red flags’ associated with the GU system?
- Painless macroscopic haematuria
- Haematuria and UTI symptoms but sterile urine
- Testicular swelling
- Abdominal mass thought to be from GU tract
- Hard irregular prostate
- Normal prostate but rising/raised age specific PSA with/without LUTI symptoms
- Symptoms and high PSA
- Postmenopausal bleeding
- Persistent intermenstrual bleeding
- Palpable pelvic mass/cervical lesion/vulval mass
What are the symptoms of prostate enlargement? (both irritative and obstructive)
IRRITATIVE - urgency, dysuria, frequency, nocturia
OBSTRUCTIVE - reduced force of stream, hesitancy
Can also cause perineal pain
What is loin pain? What are the causes of loin pain?
Pain at side of back below the ribs
CAUSES - pyelonephritis, renal calculi, hydronephrosis, renal tumour, renal abscess
What are the causes of haematuria?
UTI UT calculi Bladder carcinoma Glomerulonephritis Renal carcinoma Benign prostatic hypertrophy Prostatic carcinoma
- consider bleeding disorders/ anticoags
What are the (i) exocrine secretions (ii) functions of the salivary glands?
- salt and water - moisten food
- mucous - lubrication
- amylase - polysaccharide-digesting enzyme
What are the (i) exocrine secretions (ii) functions of the oesophagus?
(i) mucous - moves food to stomach by peristaltic waves, lubrication
What are the (i) exocrine secretions (ii) functions of the stomach?
(i) HCl - solubilsation of food particles, kill microbes Pepsin - Protein digesting enzyme
Mucous - lubricate and protect epithelial surface
What are the (i) exocrine secretions (ii) functions of the small intestine?
(i) enzymes - food digestion
Salt and water - maintain fluidity of luminal contents
Mucous - lubrication
What are the (i) exocrine secretions (ii) functions of the large intestine?
Mucous for lubrication
(ii) storage and concentration of undigested matter, mixing and propulsion of water for defecation
What are the (i) exocrine secretions (ii) functions of the pancreas?
Enzymes - digest carbs, fats, proteins and nucleic acids
Bicarbonate - neutralise HCl entering small intestine from stomach
What are the (i) exocrine secretions (ii) functions of the liver?
Bile salts - solubilise water-insoluble fats
Bicarbonate - neutralise HCl entering small intestine from stomach
Organic waste products and trace materials - elimination in faeces
What are the (i) exocrine secretions (ii) functions of the gallbladder?
Store and concentrates bile between meals
What are the 5 major physiological processes?
- MOTILITY
- propulsion of ingested food from mouth to rectum
- mixing and reduction in particle size to optimise time for digestion and absorption - SECRETION
- salivary glands, stomach, small intestine, pancreas, liver
- add fluid, electrolytes, enzymes and mucous - DIGESTION
- ingested food is digested into absorbable molecules - ABSORPTION
- nutrients, electrolytes and water are absorbed from intestinal lumen into bloodstream - EXCRETION
What are the types of (i) immunological and (ii) non-immunological defence mechanisms?
(i) mucosal immune system (GALT)
- organised aggregates of lymphoid tissue (Peyer’s patches)
- diffuse populations of immune cells (lymphocytes and mast cells)
Protection against microbial pathogens and mediate immunological tolerance to dietary substances and gut bacteria
(ii) gastric acid, mucin, peristalisis and the epithelial cell layer barrier
There are 7 layers of the GI tract, list what each layer consists of.
1 = muscularis mucosae, epithelium, lamina propria
- Submucosa
- Submucosal plexus
- Circular muscle
- Myenteric plexus
- Longitudinal muscle
- Serosa
What are the three types of mucosa? Describe where appropriate.
- Epithelial layer (villi and/or crypts - both increase SA of GI tract) more vili = greater absorption and vice versa
- Lamina propria = underlying loose connective tissue with capillaries, enteric neurones and immune cells
- Muscularis mucosae (lamina muscularis) - thin smooth muscle layer of the mucosa - deepest layer of mucosa
Describe the submucosa.
Loose connective tissue Larger blood vessels Lymphatics Secretory glands Enteric neurones in the submucosa - submucosal plexus
Describe the muscularis externa.
Inner layer of circular muscle
Outer layer of longitudinal muscle
Enteric neurones between the muscle layers - myenteric plexus
Describe the serosa.
Is an outer layer of connective tissue covered with squamous epithelial cells
What is the intrinsic component of the GI tract? Describe this component.
Enteric Nervous System
- SUBMUCOSAL PLEXUS (meissner’s plexus): small and large intestine (mainly regulate glandular, endocrine and epithelial secretions)
- MYENTERIC PLEXUS (Auerbach’s plexus): between circular and longitudinal muscle layers throughout GI tract (mainly motor neurons)
What are the 3 main topics/types of GI reflexes? Give a few examples for each.
- Reflexes integrated within the enteric nervous system
- secretion, peristalisis, mixing, local inhibitory actions - Reflexes from GIT to prevertebral symp ganglia and back to GIT
- transmit signals to other areas of GIT e.g. gastrocolic reflexes (stomach - colon); enterogastric reflexes (stomach and colon inhibiting gastric motility); colonoileal reflexes (inhibition of ileal emptying) - Reflexes from the GIT to brain stem/SC and then back to GIT
- (a) from stomach/duodenum to brainstem and back to stomach to control gastric motor and secretory activity
- (b) pain reflexes causing general inhibition of entire GIT
- (c) defecation reflexes from the colon and rectum that travel via the SC back to produce powerful colonic, rectal and abdominal contractions
What is the (i) source (ii) target (iii) action of the GI hormone GASTRIN?
(i) G cells in the antrum of the stomach
(ii) Parietal cells in body of stomach
(iii) Increases H+ secretion and stimulates the growth of gastric mucosa
What is the (i) source (ii) target (iii) action of the GI hormone CHOLECYSTOKININ (CCK)?
(i) I cells in the duodenum and jejunum: neurons in ileum and colon
(ii) pancreas and gallbladder
(iii) increases enzyme secretion and increases contraction
What is the (i) source (ii) target (iii) action of the GI hormone SECRETIN?
(i) S cells in small intestine
(ii) pancreas and stomach
(iii) increases HCO3- and fluid secretion by pancreatic ducts. Also decreases gastric acid secretion
What is the (i) source (ii) target (iii) action of the GI hormone GASTRIC-INHIBITORY PEPTIDE (GIP)?
(i) K cells in duodenum and jejunum
(ii) pancreas and stomach
(iii) exocrine: decreases fluid absorption
endocrine: increases insulin release
Decreases gastrin release
What 4 international documents refer to health as a human right?
- WHO constitution (2006)
- Universal Declaration of Human Rights (UN) (1948) - standard of living adequate for health and well being of himself
- International Covenant on Economic, Social and Cultural Right (1976) - highest attainable standard of physical and mental health
- UN Convention on the Rights of the Child (1990) - child has highest attainable standard of health
Why are infectious diseases a global ethical issue? (HINT: theres 4 points)
- ‘Unrivalled consequences’ - huge impact on history and health
- Control measures in place raise important Qs re violation of important rights (to freedom of movement, privacy and informed consent)
- Justice
- Do not respect boundaries
What are the 6 conditions that must be met for isolation and quarantine to be ethically correct?
- Must be effective in controlling the disease
- If less restrictive measures achieve the same effect then you should use them
- The consequences of NOT quarantining must be severe
- They must be implemented in an equitable manner
- Must be minimally burdensome
- Those contained must receive compensation
What are the 3 good moral reasons for carrying out research in developing countries?
- Global health inequalities
- Disproportionate burden of disease
- Value of research in developing countries
What was the problem, highlighted in the 1997 AZT trials, that can be posed by the “control” used in some drug trials?
What is the correct control to use?
- standard treatment or a placebo?
What does section 33 of the declaration of Helsinki say about the use of placebo?
A new intervention must be tested against those of the best proven intervention(s), except where no proven intervention exists, with the use of placebo or where no intervention is acceptable
During war, what is the rules of medical ethics? What are medical personnel protected by?
Their primary obligation is to their pts, to preserve health and save life
They are protected under Red Cross and Red Crescent, and also red crystal
How best they may medical students ethically address the dilemmas they face in resource-poor countries?
- Staying within their competence
- Maintaining ethical standards
- Develop ‘cultural competence’
4 Minimise burden on host country and healthcare system
What are the 3 ethical issues encountered during the medical response to the 2014 Ebola outbreak?
- Health and human rights
- Quarantine/isolation
- Access to medication
With regards to the ebola outbreak, why was Health and Human rights an ethical issue?
Ebola outbreak was centred around some of the poorest countries in the world
- lack of basic healthcare facilities to treat pts and lack of basic disease response infrastructure
Therefore should Western healthcare workers working in the affected countries be transferred back to western healthcare facilities
ALSO who should receive the limited treatments
With regards to the ebola outbreak, why was Quarantine/Isolation an ethical issue?
Should healthcare workers returning from ebola treatment centres be quarantined?
What structures are found in the (i) Right upper quadrant (ii) Left upper quadrant (iii) Right lower quadrant (iv) Left lower quadrant?
(i) Liver and gall bladder
(ii) jejunum
(iii) Ileum, caecum, appendix
(iv) sigmoid colon
Describe the skin of the abdomen. What actually is the umbilicus?
Skin is loosely attached except at umbilicus allowing movement and distension
Natural lines of cleavage in the skin are constant and run down and forwards - almost horizontally round the trunk
The umbilicus is a ‘scar’ representing the sit of attachment of the umbilical cord in the fetus
What are the 2 layers of fascia in the abdomen?
They are 2 layers of the superficial fascia, there is no definitive deep fascia
- CAMPER’s fascia - a superficial fatty layer
- SCARPA’s fascia - a deeper membranous fascia
What is the purpose of the fascia?
It is ‘packing tissue’ allowing the movement of structures in relation to each other, but without being restrictive
- some fascia provides muscle attachment
What happens to the 2 layers of fascia in the scrotum?
Camper’s is replaced by dartos muscle in the scrotum
Scarpa’s extends into the penis and scrotum but fuses with the fascia lata of the thigh below the inguinal ligament, and also with the perineal body
What are the 2 types of fascia deep to the muscle layer? Describe them both.
- TRANVERSALIS
- thin layer which lines the transversus abdominus muscle, is continuous with a similiar layer lining the diaphragm and iliacus muscle - EXTRAPERITONEAL
- thin layer which contains a variable amount of fat and lies between the transversalis fat and the parietal peritoneum
What is thoracolumbar fascia?
Passes from iliac crest to 12th rib and is in 3 layers (ant, middle, post)
Surrounds the back muscles and fuse together to give origin to the transversus abdominus and internal oblique
it is thicker than the other deeper fascial layers - it is an almost aponeurotic layer of fascia
What are the 4 muscles of the anterior abdominal wall? (from superficial to deep)
- External oblique
- Internal oblique
- Transversus abdominus
- A vertical muscle rectus abdominus (and pyramidalis)
What are the 3 functions of the anterior abdominal wall muscles?
- Support abdominal contents and raise intra-abdominal pressure, withstanding pressure from descent of the diaphragm
- Supporting vertebral column, flexing, laterally flexing and rotating the trunk against resistance
- Respiration
What are the attachments and nerve supply of the external oblique?
Attaches to lower 8 ribs, lateral lip of iliac crest, aponeurosis to linea alba via rectus sheath - which forms the inguinal ligament
Fibres pass down and medial
Nerve supply = T7 to 12
What are the attachments and nerve supply of the internal oblique?
Thoracolumbar fascia, iliac crest, lateral 2/3rds of inguinal ligament, lower 3/4 ribs and CC’s, aponeurosis to linea alba vi rectus sheath, pubic crest behind the superficial inguinal ring via conjoint tendon
Fibres pass up and medial to ribs but down to conjoint tendon
NERVE SUPPLY = T7 - 12 plus L1 via iliohypogastric nerve fibres that form the conjoint tendon
What can injury to the iliohypogastric nerve result in?
It may weaken the conjoint tendon and predispose to inguinal hernias
What are the attachments and nerve supply of transversus abdominus?
Attaches to throacolumbar fascia; iliac crest; lateral 1/3 or half of inguinal lig, lower 6 ribs and CC’s, aponeurosis to linea alba via rectus sheath, pubic crest behind inguinal ring via conjoint tendon
Fibres pass transversely to ribs, linea alba and conjoint tendon
NERVE SUPPLY = T7-12 plus L1 of iliohypogastric nerve to the fibres that form the conjoint tendon
What is the conjoint tendon?
Formed from the aponeuroses of int. oblique and transversus abdominis
Attaches to the pubic crest and pectineal line behind the superficial inguinal ring, therefore supporting the ring
What are the attachments and nerve supply of rectus abdominis?
CC’s of ribs 5-7, xiphoid, pubic symphysis, pubic crest and pectineal line
Fibres pass vertically but are interspersed with tendinous intersections
NERVE SUPPLY = T7 to 12
What is the (i) source (ii) target (iii) action of the GI hormone GLUCAGON?
(i) alpha cells of pancreatic islets of langerhans
(ii) liver
(iii) increases glycogenolysis and gluconeogenesis
What is the (i) source (ii) target (iii) action of the GI paracrine SOMATOSTATIN?
(i) D cells of stomach and duodenum. Cells of pancreatic islets
(ii)(iii) STOMACHmach - decrease Gastrin release
INTESTINE - increase fluid absorption and decrease fluid secretion
PANCREAS - decrease endocrine and exocrine secretions
LIVER - decrease bile flow
What is the (i) source (ii) target (iii) action of the GI paracrine HISTAMINE?
(i) endocrine cells of the gastric mucosa
(ii) stomach
(iii) stimulates H+ secretion from parietal cells in stomach
What is the (i) source (ii) target (iii) action of the GI neurocrine ACETYLCHOLIINE?
(i) cholenergic neurones
(ii)(iii) SMOOTH MUSCLE - contraction in GI wall and relaxation of sphincters
SALIVARY GLANDS, STOMACH and PANCREAS all to increase secretion
What is the (i) source (ii) target (iii) action of the GI neurocrine NORADRENALINE (norepinephrine)?
(i) adrenergic neurones
(ii)(iii)
SMOOTH MUSCLE - relax GI wall
SALIVARY GLANDS - increases secretion
What is the (i) source (ii) target (iii) action of the GI neurocrine VASOACTIVE INTESTINAL PEPTIDE (VIP)?
(i) enteric nervous system
(ii)(iii)
SMOOTH MUSCLE - relaxation
PANCREAS and INTESTINE - increases secretion
Describe the muscle pyramidalis, where are its attachments?
Small triangle anterior to rectus abdominus
From the pubic crest to the linea alba
Describe the rectus sheath, be sure to mention what happens to them in the midline and the clinical significance of this.
Each RA is enclosed anteriorly and posteriorly between the bilaminar aponeuroses of the external oblique, internal oblique and transversus abdominus - forming the rectus sheath
In the midline they fuse as the linea alba, it is relatively avascular therefore good for entering the abdomen but poor healing
What is the inguinal region? What does it contain?
A tunnel with 2 openings: deep and superficial rings that are each protected by 2 of the 3 muscles
CONTAINS - vas deferens and testicular vessels in males - round lig in females
plus ilioinguinal nerve and the genital branch of genitofemoral nerve
Describe the (i) Superficial inguinal ring (ii) Deep inguinal ring.
(i) A triangle within ext. oblique and its base on pubic crest. Medial and lateral crura and is supported from behind by the conjoint tendon
(ii) Opening in/evagination of transversalis fascia
Overlain anteriorly by int. and ext. oblique
Lies lateral to inf. epigastric vessels
What is the (i) anterior (ii) posterior (iii) roof (iv) floor boundaries of the inguinal canal?
(i) ANT: ext. oblique with int. oblique laterally
POST: conjoint tendon medially; transversalis fascia laterally
ROOF: arching fibres of int. oblique and transversus abdominis
FLOOR: inrolled lower edge of inguinal lig, stretched medially by lacunar lig.
What are the mechanics of the inguinal canal and surrounding muscles upon coughing and straining? (micturition, defecation, parturition)
The arching lowest fibres of the internal oblique and transversus abdominis contract therefore flattening out the arched roof so that it’s lowered towards the floor. The roof may actually compress the contents of the canal against the floor so the canal is virtually closed
In males what is the inguinal region particularly susceptible to?
development of hernias
What is the definition of a hernia? Where does an (i) inguinal (ii) femoral hernia usually appear on the body?
A protrusion of a viscus through the wall of its containing cavity
(i) above and medial to the pubic tubercle
(ii) below and lateral to pubic tubercle
What is the difference between a direct and an indirect inguinal hernia?
DIRECT - through the posterior wall of inguinal canal MEDIAL to inf. epigastric vessels
INDIRECT - through deep inguinal ring LATERAL to inf. epigastric vessels
What are the (i) medial (ii) lateral (iii) inferior borders of Hesselbach’s Inguinal triangle?
(i) lateral edge of rectus abdominis muscle
(ii) inf. epigastric vessels
(iii) inguinal ligament
What are the muscles that comprise the posterior abdominal wall? What is their function(s)?
Quadratus lumborum, Psoas major (with minor possibly overlying) and Iliacus
FUNCTIONS
- quadratus stabilises the 12th rib for diaphragmatic movement in respiration, may weakly laterally flex the trunk along with psoas minor if present
- psoas major and iliacus pass to lesser trochanter together and are powerful hip flexors
What is the attachments and nerve supply of quadratus lumborum?
Attachments = iliac crest, iliolumbar ligament and L5 transverse process to 12th rib and L1-4 transverse processes NERVE = T12 and L1-4
What is the attachments and nerve supply of psoas major?
Transverse processes, bodies and IV discs of T12 and L1-5 to the trochanter of femur (with iliacus)
NERVE = L1-3
What is the attachments and nerve supply of psoas minor? What % of people is this muscle absent in?
T12/L1 bodies to pectineal line and iliopectineal eminence on pelvic bone
NERVE = L1
Absent in 50% ppl
What is the attachments and nerve supply of Iliacus?
Iliac fossa to lesser trochanter of femur (w. psoas)
NERVE = femoral nerve L2, 3, 4
What is the femoral sheath an extension of? What does it surround?
An extension of the abdominal transversalis fascia
Surround femoral artery, vein and canal
What does the femoral canal contain? What is the boundaries of the femoral canal?
Contains Cloquet’s lymph node that receives directly from glans of penis or clitoris
BOUNDARIES:
- medial = lacunar ligament
- lateral = femoral vein
- posterior = pectineus/pectineal lig for ring
- anterior = inguinal lig
Describe the nerve supply of the skin of the abdominal wall.
T7-11 pass just inf to ribs and then into the abdominal all at the costal margin
T12 is the subcostal nerve
L1 contributes to the lumbar plexus but is found in iliohypogastric and ilioinguinal nerves
They pass inferomedially round abdomen between int oblique and transversus abdominus
What are the dermatomes at (i) T7 (ii) T10 (iii) T12? Where do each of them refer pain to?
(i) epigastric - RP stomach and oesophagus
(ii) umbilical - RP appendix, gonad, small intestine
(iii) suprapubic - RP lower colon, bladder, uterus
What is the nerve supply of the abdominal wall muscles?
T7 - 12 and L1 as iliohypogastric and ilio-inguinal nerves
If surgically splitting rectus abdominis, what way must its fibres be pushed? Why is this the case?
Laterally - towards the nerves to avoid denervation
What does the iliohypogastric nerve pierce? Where does the ilio-inguinal nerve emerge? Where do they both end?
Pierces the ext. oblique aponeurosis above the superficial inguinal ring
Ilio-inguinal emerges through the superficial ring
End by supplying the skin just above the inguinal lig
What may nerve injury of the iliohypogastric cause?
May weaken the conjoint tendon and predispose to hernia as it supplies the fibres of internal oblique and transverse abdominis that form the tendon
Where are appendicectomy incisions made? What is the risk of extending the incision laterally?
Made 1/3 of the way up the line from the ASIS to umbilicus at McBurney’s point
Extending the incision laterally may put the iliohypogastric nerve at risk, with the possible consequence of weakening the conjoint tendon…hernia
What is the arterial supply of the abdominal wall?
The nerves are accompanied by branches of the intercostal and lumbar arteries
- but augmented by the superior, inferior and superficial epigastrics
- as well as the superficial and deep circumflex iliacs
Describe the superior epigastric artery, ensuring to mention its route within the body.
Branch of internal thoracic
- enters upper part of rectus sheath between sternal and costal origins of the diaphragm
- descends behind rectus muscle, supplying the upper central part of the anterior abdominal wall
- anastomoses ith the inf. epigastric (collateral circulation for obstructed aorta)
Describe the inferior epigastric artery, ensuring to mention its route within the body.
Branch of ext. iliac
- runs up and medially along medial side of deep inguinal ring, pierces transversalis fascia to enter the rectus sheath anterior to the arcuate line
- ascends behind the rectus muscle, supplying the lower central part of anterior abdominal wall
- anastomoses with superior epigastric
Describe the deep circumflex iliac artery, ensuring to mention its route within the body.
Branch of external iliac, just above the inguinal ligament.
- runs up and laterally towards ASIS, then continues along iliac crest
- supplies the lower, lateral part of the abdominal wall
Where does the sup. epigastric and the superficial circumflex iliac arteries arise from? What do they supply?
From the femoral
- just below the inguinal ligament
- they supply the lower abdominal wall
Where/what do the superficial epigastric and superficial circumflex iliac veins drain to?
The proximal end of the great saphenous vein
- along with superficial and deep ext. pudendal (varicose vein surgery)
What may obstruction of the portal vein cause?
Venous back pressure into the veins of the abdominal wall
- resulting in a Caput Medusae
What is the superficial lymphatic drainage of the (i) anterior (ii) posterior abdominal wall?
(i) ABOVE umbilicus to the axillary nodes
BELOW umbilicus to the superficial inguinal nodes
(ii) ABOVE iliac crests to axillary nodes
BELOW iliac crests to superficial inguinal nodes
Where do the (i) axillary nodes (ii) superficial inguinal nodes empty into?
(i) The subclavian lymph trunk
(ii) deep inguinal to ext. iliac to para-aortic nodes
For what type of surgery are the following incisions used; (i) Kocher (ii) Thoraco-abdominal (iii) Midline (iv) Muscle splitting loin (v) Pfannenstiel (vi) paramedian?
(i) removal of gall bladder
(ii) accessing oesophagus
(iii) rapid access through linea alba (poor healing)
(iv) appendicectomy - muscle split in direction of their fibres rather than incised so good strong healing
(v) gynaecological ad other pelvic procedures
(vi) avoiding midline for better healing, RA fibres reflected laterally towards nerve supply
What is the difference between the peritoneum in males and females? What is the clincial significance of this?
It is a closed cavity in males but in females there’s a communication with the exterior through the uterine tubes, the uterus and the vagina
- may allow the spread of infection from the exterior to inside the peritoneal cavity
What is the extraperitoneal tissue/fascia? What is this structure like around the kidneys?
A layer of connective tissue between the parietal peritoneum and the fascial lining of the abdominal and pelvic walls
- in kidneys area it contains a large amount of fat hich supports the kidneys
What 3 structures does the peritoneum form?
Omenta
Mesenteries
Ligaments
What is the omenta? Describe both the Greater and Lesser omentum.
2-layered folds of peritoneum that connect the stomach and the 1st part of duodenum to other structures
GREATER = derived from dorsal mesentery, from greater curvature of stomach and 1st part of duodenum. Contains fat and overlies transverse colon and much of small intestine
LESSER = passes from lesser curavture of stomach and 1st part duodenum to inf. border of th eliver
What are mesenteries? What are the 3 types?
Double-layered peritoneal folds that attach viscera to the posterior abdominal wall. They are conduits for vessels, nerves and lymphatics
The mesentery
Transverse mesocolon
Sigmoid mesocolon
What is the hepatoduodenal ligament? What does it contain?
The free edge of the lesser omentum
- containing the portal vein, hepatic artery and bile duct
Describe the mesentery, ensuring to mention where it is located.
A fan shaped double-layered fold of peritoneum that connects the jejunum and ileum to the posterior abdominal wall
- base starts just left of L2 and passes obliquely downwards to the right, ending just above the right sacro-iliac joint, is about 20cms long
- crosses the 3rd part of the duodenum, the aorta and IVC, r. gonadal vessels and r. ureter
- contains branches of the SMA and SMV with nerves and lymphatics
What is the difference between the anastomotic arcades of the mesentery of the (i) jejunum (ii) ileum?
(i) few arcades with long vasa recta
(ii) many arcades with short vasa recta
What is the sigmoid mesocolon? What is its location? What is its function?
the double-layered fold of peritoneum that connects the sigmoid colon to the posterior abdominal wall
- roof is in the left iliac fossa, crossing the bifurcation of the left common iliac vessels and the left ureter
- transmits the sigmoid branches of the inferior mesenteric vessels, plus nerves and lymphatics
What is the transverse mesocolon? Where is it located? What does it divide the peritoneal cavity into?
Suspends the transverse colon from the posterior abdominal wall
- its root is just inferior to the pancreas and carries branches of the middle colic vessels
- divides the cavity into supra and infra
SUPRA = liver stomach and spleen
INFRA = jejunum, ileum, asc. and desc. colon
What is the clincial significance of peritoneal pouches, recesses, spaces and gutters? Name one important pouch.
Places which can house pus, blood, or allow the spread of either
Morison’s pouch - the right posterior subphrenic OR hepatorenal space
What is the (i) median umbiliac fold (ii) medial umbilical folds (iii) lateral umbilical folds?
(i) contains the urachus which extends from the urinary bladder to the umbilicus
(ii) raised by the obliterated umbilical arteries, extending from the int. iliac arteries to the umbilicus
(iii) raised by the inferior epigastric arteries, extending from the deep inguinal rings on each side of the arcuate lines
Why are peritoneal ligaments not really ligaments?
They are actually two layered folds of peritoneum which connect two organs together
What organs are retroperitoneal? (HINT: sad pucker)
Supradrenal glands
Aorta/IVC
Duodenum (excl. proximal 1st seg)
Pancreas (except tail) Ureters Colon (asc and desc) Kidneys oEsophagus Rectum
and Bladder
What organ is truly intraperitoneal? Why is this the case?
OVARY
- it has absorbed its peritoneal covering
What 4 things is the parietal peritoneum sensitive to?
Pain
Temperature
Touch
Pressure
What is the nerve supply to the peritoneum (i) lining the anterior abdominal wall (ii) diaphragmatic (iii) parietal in pelvis?
(i) T7-12 and L1
(ii) phrenic nerves C3,4,5
(iii) obturator nerve (L2,3,4)
What 2 things is the visceral peritoneum sensitive to?
Stretch and tearing
What is derived from the (i) ectoderm (ii) mesoderm (iii) endoderm?
(i) neural tube and body wall
(ii) CV and MS, and the body cavities (coeloms)
(iii) GI, respiratory and repro
With regards to the notochord, what happens on day 17 of embryological development?
Notochord burrows from primitive node (between ecto and endoderm)
- undergoes a series of developmental changes but becomes a plate that induces the overlying ectoderm to become the neural plate
What does cephalo-caudal and lateral folding of the trilaminar disc create?
Endodermal tube of pharynx and oesophagus
Stomach and intestinal trcat
Glands associated with the GI tract
What is (i) Exomphalos (ii) Gastroschisis?
(i) failure of intestine to return to abdomen, lies within peritoneum and amnion, in umbilical cord
(ii) failure of abdominal wall, contents not covered by peritoneum or amnion
What are the main functions of GI tract motility?
- Involves contraction adn relaxation of GI wall and sphincters
- Grinds, mixes and fragments ingested food
- prepares food for digestion
- propels food along the GI tract - All of the contractile tissue is smooth muscle (excl. pharynx, upper 1/3 oesophagus and ext. anal sphincter)
What are the 2 types of smooth muscle? What type contains gap junctions?
- MULTIUNIT
- SINGLE UNIT - what is mainly found in the GI tract
- contain gap junctions = single unit
Describe the calcium activation of myosin in smooth muscle.
Calcium binds to calmodulin forming a calcium calmodulin complex which in turn activates MLCK, which phosphorylates myosin - activating it.
What is the LATCH STATE in smooth muscle contraction?
It maintains high tension
- decrease in detachment rate of myosin heads, maintaining cross bridge binding with reduced ATP consumption
- without expending much energy you get ALOT of contraction
What happens in smooth muscle relaxation?
A decrease in Ca results in calmodulin being released from the calcium calmodulin complex. This inactivates the MLCK which as a result dephophorylates the myosin rendering it inactive.
What is the origin/initiation of slow waves in smooth muscle?
The interstitial cells of Cajal (ICC) are pacemaker cells of the GI tract and are abundant in the myenteric plexus
What is the intrinsic rate of the slow waves? Ensuring to mention precise values for both the stomach and duodenum.
It varies from 3 - 12 per minute
STOMACH = 3 waves per minute
DUODENUM = 12 waves per minute
With regards to slow waves in smooth muscle, what affect does neuronal and hormonal input have?
It does not affect the frequency of the slow waves BUT they influence the action potential frequency i.e. the strength of the contraction
Smooth muscle cells respond to _______ ______ depolarisation with increased ___ channel ______ __________.
slow wave
calcium
open probability.
What is the role of interstitial cells of Cajal (ICC) in slow wave generation, naming the (i) inhibitory motor neurone (ii) excitatory motor neurone substances.
(i) Nitric oxide, ATP, VIP (vasoactive intestinal peptide)
(ii) ACh, substance P
What are the steps in slow wave generation?
Depolarisation due to the cyclical opening of voltage gated Ca2+ channels:
- Increase in the intracellular Ca2+ concentration
- Opening of Ca2+ dependent K+ channels
- Increased K+ permeability leads to slow hyperpolarisation
- Voltage gated Ca2+ channels close and intracellular Ca2+ concentration falls
- Ca2+ dependent K+ channels close
- Voltage gated Ca2+ channels open
What are the 3 things that stimulate depolarisation?
Stretch
Acetylcholine
Parasympathetics
What 2 things stimulate hyperpolarisation?
Norepinephrine
Sympathetics
What are the 3 functions of the process of chewing?
- Mixes food with saliva
- lubrication, mucin (glycoprotein) acts as lubricant - Reduces size of food particles
- facilitate swallowing - Mixes food components with digestive enzymes, e.g.
- Carbohydrate with salivary amylase for carb digestion
- fat with lipases for lipid digestion
For chewing, there are both voluntary and involuntary components. Describe the involuntary component.
Reflexes are initiated by food in the mouth
- sensory information relayed from mechanoreceptors to the brain stem initiates a reflex pscillatory pattern of activity in chewing muscles
What are the 3 phases of swallowing?
- Oral phase
- Pharyngeal phase
- Oesophageal phase
What is the (i) afferent (ii) efferent pathway of swallowing? Where is the swallowing centre located?
(i) sensory info from touch receptors near pharynx
(ii) involves cranial innervation of pharynx and upper oesophagus and vagal motor innervation of lower oesophagus
- in the medulla and lower pons
What are the 6 steps involved in the swallowing reflex?
- Upper oesophageal sphincter opens to allow the bolus of food to enter the oesophagus
- Upper oesophageal sphincter closes
- Primary peristaltic contraction mediated by swallowing reflex involves a series of coordinated contractions creating a region of high pressure behind bolus
- Lower oesophageal sphincter opens mediated by peptidergic nerves in vagus releasing VIP
- Receptive relaxation of the orad region of the stomach
- Lower oesophageal sphincter closes
What is achalasia? What does it result in for patients? How does it occur?
It is an absence of relaxation
Results in dysphagia (difficulty swallowing)
Occurs by failure of lower oesophageal sphincter to relax (from loss of neurons which regulate this sphincter by releasing VIP) or impaired peristalsis in distal regions
