Exam 4 Anatomy 403

digestive processes

break down food particles in chyme that the body can work with on a cellular level

-ingestion, secretion, mixing and propulsion, mechanial and chemical digestion, absorption, defacation

GI tract organs

(alimentary canal)

Mouth

Pharynx

Esophagus

Stomach

Small Intestine

Large Intestine

Accessory Digestive Organs

Teeth

Tongue

Salivary Glands

Liver

Gallbladder

Pancreas

Develop and organization of gut

The gut starts out as a single embryological gut tube, rotates as it grows

-this gut persists into adulthood, organization of regions important

-regional and neurovascular supply relationships maintained in developed gut

Regions of gut

Foregut (celiac trunk)

Midgut (SMA)

Hingut (IMA)

Organs in the Foregut

Esophagus (abdominal)

Stomach

Prox 2/3 Duodenum

Accessory Organs:

Liver and Gallbladder

Spleen

Pancreas

Organs in Midgut

Distal 1/3 of Duodenum

Jejunum

Ileum

Cecum (appendix)

Ascending Colon

prox 2/3 Transverse Colon

Organs in Hindgut

Distal 1/3 transverse colon

Descending Colon

Sigmoid Colon

Rectum

Anus

Celiac Trunk Branches

Common Hepatic

-R gastric (R lesser curvature)

-Gastroduodenal--> R gastro-omental (greater curvature)

-Proper Hepatic (liver)

L gastric a. (L lesser curvature)

Splenic--> Left Gastro-omental (greater curvature)

Super Mesenteric Artery

Arterial Supply of Gut

Colic Branches

Jejunal Branches

Ileal Branches

Inferior Mesenteric Artery

Arterial supply of Gut

Colic Branches

Superior Rectal a.

Hepatic Portal Vein

Drains to Liver- all venous blood from gut processes in liver before returning to systemic circulation

-SMV

-IMV

-Splenic vein

Portal Caval anastomoses

- small connections between portal v. tributaries of vena cava

- walls of organs

- body wall around umbilicus

- emergency route for blood if liver has blockages

Flow of Blood in Gut (arteries)

1) Celiac Trunk

2) L Gastric

3) Common Hepatic

4) Proper Hepatic

5) R Gastric

Flow of Blood in Gut (veins)

1) L Gastric

2) R gastric

3) Hepatic Portal Vein

4) Splenic

5) SMV

6) IMV

all drain into IVC

Enteric Nervous System

-neurons located in gut

-innervate digestive organs

Autonomic Motor

-sympathetic and parasympathetic nervous system

Visceral Sensory

Submucosal (Meissner's) Plexus

Where: Submucosa (connective tissue layer deep to mucous membrane)

For: mucosal glands

--secrete mucosa and digestive chemicals in lumen of GI tract

Myenteric (Auerbach's) Plexus

Where: Muscularis (muscular layer)

For: Gut Motility

-move contents through GI tract (peristalsis)

Sympathetic Supply of Gut

Thoracic Splanchnic nn. (greater and lesser)--> Synapse in prevertebral ganglia--> Foregut and Midgut Viscera

Lumbar Splanchnic nn--> synapse in prevertebral ganglis--> Hingut Viscera

-all symp innervation originates in spinal cord and travels to symp chain

-1st splanchic nn synapses at prevertebral ganglia

-2nd neuron follows blood vessels to target organ

Sympathetic Innervation of Gut

*Inhibit Digestion by slow production of digestive juices*

Pre-ganglionic fibers in splanchnic nn

Post-ganglionic fibers in aortic and peri-arterial plexuses

Parasympathetic Supply of Gut

Posterior/Anterior Vagal Trunks (Vagus nerve)--> synapse in enteric ganglia--> foregut and midgut viscera

Pelvic Splanchnic nn (S2-4) --> synapse in enteric ganglia --> hingut viscera

-Vagus nerves carries preganglionic fibers for foregut/midgut; pelvic splanchnic for hindgut

-synapse at enteric ganglia within walls of small organ its innervating

Parasympathetic Innervation of Gut

*speed up digestion, stimulates peristalsis*

Pre-ganglionic fibers in aortic and peri-arterial plexuses

Post-ganglionic fibers in myenteric/submucosal plexuses

Sensory Innervation of Gut

-Enteric Reflex loops

-follow symp and parasymp pathways back to spinal cord

--synapse in same region as somatic sensory

Referred pain: visceral pain felt as somatic pain in body wall

-Foregut: epigastric

-Midgut: peri-umbilical

-Hingut: hypogastric

Layers of GI Tract

Superficial to Deep

1. Serosa/Adventitia

2. Muscularis

3. Submucosa

4. Mucosa

Mucosa

Deepest layer

-Epithelial Layer

-Areolar Connective Tissue

-Smooth muscle

Epithelial layer (mucosa)

Mouth/pharynx/esophagus: stratified squamous epithelium (protection)

Stomach/intestine: simple columnar epithelium (tight seal)

--replaced 5-7 days

Areolar Connective Tissue and Smooth muscle (mucosa)

Areolar: blood and lymphatic vessels (MALT)

Muscle: -folds mucosa

-expose absorptive cells to GI contents

Submucosa

-Connective Tissue Layer (collagen, nerves, blood vessels)

-Submucosal Plexus

Submucosal Plexus (submucosa)

part of enteric nervous system

-Autonomic neurons

--Symp (splanchnic nn)

--Parasymp (Vagus)

-Enteric neurons

-regulates mucosal movement (smooth muscle), vasoconstriction, secretory glands of mucosa

Muscularis

Upper GI tract: Mouth/pharynx/prox 2/3 esophagus

--skeletal muscle (swallowing)

Lower GI tract: Smooth muscle

-Longitudinal fibers (superficial): tube shorter to breakdown contents

-Circular Fibers (deep): narrow tube to propel contents

**does peristalsis**

Myenteric Plexus (muscularis)

Part of enteric nervous system

--autonomic (symp and para)

--enteric

-Control gut motility (smooth muscle)

Serosa/Adventitia

Serosa: Serous membrane surrounding GI organs

-areolar connective tissue

-epithelium (visceral peritoneum): lubricates surfaces of GI organs

Adventitia: single layer of areolar connective tissue

-no epithelium

-found in esophagus and rectum

Circular Fibers of GI tract

Propel bolus

-contract posterior

-relax anterior

Longitudinal Fibers of GI Tract

Shorten Tract

-force more circular fibers into a smaller space

-reduces force individual circular fibers must produce

Peritoneal Sac

Larges serous membrane in body (makes serous fluid)

Lines:

-walls of abdominal cavity

-walls of abdominal organs

-blood vessels and nerves traveling between

Peritoneal Sac Functions

Supports abdominal organs

-surrounds and adheres to surface

-tethers to posterior abdominal wall

Allows contraction of smooth muscle without gross movements

-prevents twisting and knots

Division of Peritoneal Sac

Visceral Peritoneum

-wall of organs

Parietal Peritoneum

-abdominal wall

Mesentery/Ligament

-tethers wall to organ

Retroperitoneal

posterior to peritoneal sac

Intraperitoneal

-protrudes into peritoneal cavity

-walls covered by visceral peritoneum

-has a mesentery

Organs that are Retroperitoneal

SADPUCKER

S-suprarenal organs (adrenals)

A- aorta and IV

D- duodenum (distal 3/4)

P-pancreas (head&body)

U-ureters and bladder

C-colon (ascending and descending)

K- kidneys

E-esophagus

R- rectum/anal canal (mid distal)

Organs that are Intraperitoneal

Stomach

Liver

Gallbladder

Spleen

Duodenum (prox 1/4)

Jejunum

Ileum

Cecum

Appendix

Transverse Colon

Sigmoid Colon

Mesenteries

2 layers of peritoneum

-tether abdominal organs to abdominal wall and each other

*passageway to organs for blood vessels, nerves, lymph vessels*

Formation of a Mesentery

1) All GI organs begin developing posterior to the peritoneal sac

2) Organs move anteriorly and press into the sac during development

3) Peritoneum pinches closed posterior to advancing organs

4) Organs rotate and mesenteries may fuse during development

5) Organs may move posteriorly after developing a mesentery

secondary retroperitoneal

organs that move posteriorly after developing a mesentery

-retain the same blood, lymph, and nerve supply as intraperitoneal

Organs that are secondary retroperitoneal

Distal 3/4 duodenum

Pancreas

Ascending Colon

Descending Colon

major peritoneal folds

1) the mesentery

2) mesocolons (transverse and sigmoid)

3) greater omentum

4) lesser omentum

5) falciform ligament

The Mesentery

-Peritoneal fold that attaches the small intestine to the posterior wall

-Superior mesenteric a, portal vein tributaries

Mesocolons

Transverse

-transverse colon to post wall

-superior mesenteric a, portal vein tributaries

Sigmoid

-sigmoid colon to post wall

-inferior mesenteric a, portval vein tributaries

**no mesentery for ascending/descending colon bc they secondarily retroperitoneal**

Greater Omentum

greater curvature of stomach to transverse colon

-many lymph nodes to combat GI infections

Lesser Omentum

-lesser curvature of stomach to liver

--by hepatogastric ligament

-Duodenum to liver

--by hepatoduodenal ligament

-Celiac trunk branches, portal v tributes

-bile duct

falciform ligament

liver to anterior wall

-pathway of obliterated umbilical vein (round ligament)

-extends to the umbilicus (belly buttone)

oral cavity boundaries

Anterior: lips (labia)

Lateral: cheeks

Superior: hard and soft palate

Inferior: mylohyoid muscle

Posterior: fauces

oral vestibule

space between cheeks/lips and gingivae

mucosa (oral cavity)

lines palate, interior cheeks and lips, gingivae, tongue

Structures of Ingestion

Lips: open to receive food, close to maintian

-orbicularis oris m

Cheeks: hold food between teeth

-buccinator m

*Facial Nerve (CN VII)*

Salivary glands

-many small glands in mucosa

3 major bilateral glands:

--Parotid- outside cavity

--Submandibular- outside cavity

--Sublingual- inside cavity

-parasymp stimulation/ symp suppression

Saliva

99.5% water

-Digestive enzymes:

--amylase: starch

--lingual lipase: triglycerides

Innervation of salivary glands

Parotid- Glossopharyngeal nerve (CN IX)

Submandibular and Sublingual- Facial Nerve (CN VII)

Mastication

crushing or grinding of food between the teeth produced by movements of jaw

Teeth

per quadrant:

2 insicors

1 canine

2 premolars

3 molars

naming starts from upper right

Structures of Teeth

Crown (visible portion), neck, root, enamel, dentine, cement, pulp cavity (neurovasculature)

Muscles of Mastication

Temporalis

Medial/Lateral Pterygoids

Masseter

*Trigeminal, V3 (CN III)*

-involved in mechanical digestion

Tongue Muscles

Intrinsic--> shape

Extrinsic--> move in cavity

Palatoglossus, Styloglossus, Genioglossus, Hyoglossus

*Glossopharyngeal (CN IX)*

-involved in mechanical digestion and mixing and propulsion

The pharynx

beginning of respiratory pathway

-mixing and propulsion

-naso, oro, and laryngopharynx

Voluntary Phase of Swallowing

extrinsic muscles of tongue push bolus into oropharynx

Involuntary phase of swallowing

"pharyngeal phase"

-breathing pauses

-soft palate activates

--Lifts (levator veli palatini)

--Tenses (tensor veli palatini)

--closes passage between oro and naso pharynxes

Involuntary phase continued

-vocal cords close

-epiglottis bends over larynx

-pharyngeal constrictors fire

Sup, Middle, Inf pharyngeal constrictor muscles (Vagus CN X)

-help propel bolus down

Esophagus

Connects pharynx to stomach

-mixing and propulsion

propulsion in esophagus (passive)

passive transport: mucosa

-lubricated: mucous

-Sturdy: nonkeratinized stratified squamous epithelium

--overlapping cells resilient to wear and tear from boluses moving through

propulsion in esophagus (active)

Active Transport: Muscularis

Longitudinal and Circular fibers

-proximal 1/3 skeletal muscle

-middle 1/3 mixed

-distal 1/3 smooth muscle

Peristalsis (esophagus)

1. Circular muscle fibers above bolus contract (push to stomach)

2. Longitudinal muscle fibers below bolus contract (to shorten and widen tube)

3. Repeat cycle, and lower esophageal sphincter relaxes to pass into stomach

Stomach

involved in secretion ,mixing and propulsion, mechanical/chemical digestion

Feautures of the stomach

4 Regions: Cardia, Fundus, Body, Plyoris

-lesser and greater curvature

Stomach Innervation/Vasculature

Parasympathetic: Vagus

Symp: thoracic splanchnics, synapse at celiac ganglion

Artery: Celiac trunk bb

Vein: portal vein tributaries

Cardia (region of stomach)

-surrounding meeting of esophagus

-home to cardiac sphincter: physiological sphincter (not a true ring)

--can cause acid reflux

Fundus (stomach region)

rounded upper portion of the stomach, usually houses lots of gases

Body (stomach region)

-has Rugae: folds in inner walls of stomach to allow expansion/surface area for digestive glands

Pyloris (stomach region)

Distal most portion of stomach

-narrows to meet duodenum, guided by pyloric sphincter (true ring of muscle)

--open small amount to regulate rate the stomach empties

Secretion in Stomach

Muscosal Epithelium cells: produces acid

Exocrine and endocrine cells arranged in Gastric Pits

--pits made by connective tissue lamina propia

Exocrine Cells (stomach)

-responsible for chemical digestion

Mucous Cells

Chief cells: pepsinogen, gastric lipase

Parietal Cells: Hydrochloric acid

Endocrine Cells (stomach)

G cells

-gastrin: stimulates gastric juice + increases gut motility

Mucous cells

-Secrete mucous

-absorb water, ions, come drugs (aspirin), alcohol

Chief cells

Pepsinogen (pepsin with HCL)

-breaks aa peptide bonds

-clump and digest milk proteins

Gastric Lipase

-triglycerides --> fatty acids and monoglycerides

Parietal Cells

Intrinsic Factor: absorb vitamin B

-Hydrochloric acid

Mixing and Propulsion in Stomach

Muscularis:

-3 layers of muscles

--longitudinal and circular and oblique

Churning: mix with acid and gastric juices

Peristalsis: move toward duodenum

Pancreas

Involved in Secretion and Chemical Digestion

-Secondary Retroperitoneal

-posterior abdominal wall behind stomach

Features of the Pancreas

Head (resting on duodenum), Neck (close to pylorus), Body, Tail (touching spleen

Pancreas Innervation/ Vasculature

-Parasympathetic: Vagus

-Sympathetic: thoracic splanchnics, synapse at celiac ganglion

-Artery: Celiac trunk bb, Super Mesenteric bb

-Vein: Portal vein tributaries

Acini

clusters of exocrine cells

-secrete digestive (pancreatic) juice through pancreatic duct

-surrounded a duct they secrete into

Pancreatic Islets

clusters of endocrine cells

-secrete hormones to regulate blood sugar

Pancreatic Juice

-Water

-Salts

-Sodium Bicarbonate

-Digestive enzymes to break down:

--starch, proteins, triglycerides, DNA/RNA

what is the function of sodium bicarbonate produced by pancrease

to neutralize acid, duodenal contents come straight from stomach and are highly acidic.

Pancreatic Ducts

Main pancreatic duct- joins with bile duct from liver to enter duodenum together

Accessory Pancreatic Duct

Major Duodenal Papilla

Where main pancreatic and bile ducts enter the duodenum

-guarded by sphincter muscle

-only opens after a meal

Liver Functions

Blood filtration, excretion, metabolism, storage, secretes bile

-secretion and chemical digestion

Liver Innervations/Vasculature

Parasymp: Vagus

Symp: thoracic splanchnics, synapse at celiac ganglion

Artery: celiac trunk bb

Vein: portal vein

Features of Liver

-gallbladder sits on inferior surface (bile storage)

Right and Left lobe, separated by falciform ligament

Falciform ligament

-separates R and L lobes of liver

-double fold of peritoneum that attaches liver to ant. abdominal wall

-has Round ligament of liver (obliterated umbilical vein) running in lower margin

Inferior Surface of Liver

Individual lobes, but part of Left lobe

-Caudate Lobe- left of IVC

-Quadrate Lobe- left of gallbladder

Porta Hepatitis: hilum of liver

Portal Triad

Through Porta Hepatitis:

portal vein, hepatic artery, bile duct

-bile duct carry bile out to GI tract

-hepatic a supplies arterial blood to liver

-portal vein drains all of digestive organs