Exam IV Study Guide Microanatomy

The digestive system performs 4 main functions:

• Ingestion – taking in food (mouth)

• Digestion

  • Mechanical (chewing, churning)

  • Chemical (enzymes breaking molecules)

• Absorption – nutrients enter blood/lymph (mostly small intestine)

• Elimination – removal of waste (large intestine → rectum)

What is the general composition of the digestive system

Inner: Mucosa - Submucosa - Muscularis externa - Serosa/adventitia : Outer

Composition of Mucosa

Epithelium lining the lumen

Lamina Propria made of Loose CT and smooth muscle

Muscularis mucosa - thin layer of smooth muscle cells

Submucosa Composition

denser CT with large blood vessel nerves

Muscularis Externa composition

lots of nerves, made of 2 layers of smooth muscle: internal sublayer (circular orientation of fibers) External sublayer (longitudinal orientation of fibers)

Serosa/Adventitia composition

thin sheet of loose CT with adipose tissue covered in simple squamous epithelium

4 Types of Tongue Papillae

1) Filiform - no taste buds (conelike)

2) Fungiform - taste buds (mushroom shaped)

3) Foliate - parallels ridges (folds)

4) Circumvallate - taste buds and serous glands (V-shaped)

What is a taste bud

tulip-shaped modification of the epithelium that contains sensory cells, supportive cells, stem cells

Organization of the esophagus

4 layers

• epithelium of stratified squamous for protection

• Muscle made of skeletal, mixed, and smooth

• Adventitia (not serosa)

Function- move food to the stomach via peristalsis

Stomach Function

store food, protein digestion, produce acid

Stomach structure

• simple columnar epithelium to secrete mucus

• made of 3 smooth muscle layers

  • oblique layer

  • inner circular layer

  • outer longitudinal layer (for churning)

Gastric Pits

forms a cavity/pouch in the surface epithelium to deliver stomach secretions

Rugae -

internal folds in an empty stomach

Gastric Glands

extend deeper - secrete the digestive substances

Parietal Cells

secrete HCl to kill bacteria and activate pepsinogen the precursor or pepsin

Chief Cells

secrete precursor of pepsin to help digest proteins

Duodenum

links to the stomach and receives the bile, pancreas digestive enzymes

Jejunum

Major site of nutrient absorption

Ileum connects to

the large intestine

Plica

folds in the intestine mucosa and submucosa

Villi

folds in the intestine epithelium

Microvilli

microprojections that aids in digestion

Enterocytes

main cells for absorption

Paneth Cells

innate immunity

Goblet Cells

secrete mucus

Enteroendocrine Cells

hormone secretion in SI

Role of large intestine

absorb water/electrolytes

solid waste formation

Unique features of LI

no villi

many goblet cells

Liver Role

detoxification of drugs, toxins and alcohol

bile production

immune function

metabolism

What cells make the liver

Hepatocytes - 80% of liver cells

Kupffer Cells of liver

macrophages immune cells

destroy old RBCs

Endothelial Cells of liver

line the sinusoids

fenestrated - leaky to allow blood exchange

Stellate cells of liver

store Vitamin A

Bile is collected from the liver

through a network of microscopic channels called bile canaliculi

Know which direction the bile runs and which direction the blood runs.

Bile: Hepatocytes - bile canaliculi - bile ducts (portal triad) (HBCBD)

Blood: Portal Triad - sinusoids - central vein (PTSCV)

Role of sinusoids in the liver

facilitate exchange between the blood and hepatocytes for detox, metabolism etc

Hepatic Artery

Triad

Oxygen -rich to the liver from the heart

Hepatic Portal Vein

Oxygen poor

comes from digestive organs to the liver

Hepatic Vein

drains out of the liver - back to the heart

Gallbladder role and location

under the liver

Role- store and concentrate bile

releases bile when fat is present

Where does the gallbladder receive its bile acid from? and where does it deliver to

Receives from liver

delivers to the duodenum (connects SI to stomach)

Gallbladder Wall structure

Mucosa - epithelium (simple columnar)

Muscularis - smooth muscle for contraction

Serosa

Roles of the pancreas

Insulin/glucagon production

Digestive - exocrine

Hormonal - endocrine

Exocrine Pancreas

Made of Acinar Cells

Make digestive enzymes

• amylase

• lipase

• protease

Delivery: secreted into pancreatic ducts and the duodenum

Endocrine Pancreas

made of islets of langerhans

Hormonal

Beta Cells - insulin

alpha cells - glucagon

Hormones are released directly into the bloodstream

Role of the kidneys

filter bloodstream

control body fluid volume

maintain acid-base

Cortex of the kidney contains

renal corpuscles

convoluted tubules

Medulla of the kidney contains

loop of henle and collecting ducts (somewhat in the cortex also)

Role of calyx in kidney

move urine out of the kidney towards the ureter

What is the renal corpuscle

site of filtration

• contains the glomerulus and glomerular capsule

Renal Tubule role (PCT)

reabsorbs water glucose and aa to the blood stream

Loop of henle role

creates a concentration gradient

• descending limb - permeable to water

• ascending limb - impermeable to water - transports salts

Distal Convoluted Tubule (DCT)

ion regulation and further reabsorption of electrolytes etc

Collecting duct

water conservation

concentrates urine

Blood flow through the kidney

Renal Artery - Segmental Arteries - Interlobar arteries - arcuate artery - afferent arteriole - glomerulus - efferent arteriole - vasa recta - interlobular vein - arcuate vein - interlobar vein

Erythropoietin

a hormone produced primarily by the kidneys that regulates red blood cell (RBC) production in the bone marrow

Where does filtration in the kidneys occur and what happens

renal corpuscle

• water ions, glucose, small things go to capsule out of blood - large things stay in bloodstream

• produces filtrate

Reabsorption is and occurs

useful substances move from the tubule back to the blood

• like water, glucose, AA, sodium

• PCT

Secretion is

waste moves from blood into the tubule

• like H+

• drugs/toxins

Composition of the renal corpuscle

1) Glomerulus

2) Glomerular Capsule (surrounds the glomerulus)