Digestive System/Urinary

Question 1

What are the different functions of the digestive system?

Answer 1

Transportion

• peristalsis: myenteric reflex
• reverse peristalsis

Physical treatment
-chewing, propulsive peristaltic contractions and local intermittent constrictive contractions

Chemical treatment
-digestive enzymes, digestive acids, and Bile

Absorption
-of digested food particles from the lumen into blood or lymph

Question 2

The tongue of higher vertebrates are derived from what pharyngeal arches?

Answer 2

3 pharyngeal arches:
Mandibular
Hyoid arch
Third pharyngeal arch

Question 3

Evolution of the tongue

Answer 3

Early- bony fish, amphibians with gills - elevation of floor plate. No muscle.
Urodeles and anurans - tongue extension that can be flipped out of mouth. Glandular feild
Reptiles/mammals: from 3 pharyngeal arches. Lingual swellings/glandular fields.
Birds - instirnisc muscle with relation to hyoid skelton movement.

Question 4

What are the layers of the gut tract?

Answer 4

Outer to inner: 
Serosa 
Longitudinal smooth muscle layer 
Myenteric plexus 
Circular smoothmuscle layer 
Meissner's plexus- submucosal 
Submecosa 
Mucosa

Question 5

Serosa

Answer 5

Outer layer of connective tissue and simple squamous epithelium of the gut tube

Continuous with mesentery
-serves as pathway for blood vessels to gut tube

Serosa is missing in some parts: esophagus

Produces a thin layer of lubricating fluid

Question 6

Myenteric and meissnes’s plexuses function

Answer 6

The enteric nervous system in the gut tract

Autonomously through intrinsic regulation and sensory reflexes

Sympathetic and parasympathetic

• para: increases GI tract activity
• sym: opposite effect.

Question 7

Where is the myenteric plexus found? And specific function?

Answer 7

Between longitudinal and circular smooth muscle layers

Controls intestinal smooth muscle
Entire length of GI tract

Increases tonic contractions
Increases rhythmic intensity of contractions
Slightly increased rate of contraction
Increased velocity of exciting waves

Question 8

What are the specific effects of meissner’s plexuses?

Answer 8

Controls GI secretion, absorption, and local blood flow

Function of inner wall within each segment of the intestine

Control local secretion, local absorption and local contraction of submucosal muscle

Question 9

Submucosa

Answer 9

Thick connective tissue layer that supports bases of compound alveolar glands

Bed of arterioles and venules that supply mucosal capillary beds

Question 10

Mucosa

Answer 10

Derived from endoderm
Single cell layer lining entire tract
Lamina propria
-loose CT, sensory nerves, blood vessels and glands
Muscularis mucosa
-thin later of smooth muscle cells that create mucosal ridges and folds

Question 11

what is the structure of the primitive nephron? what organism are they found in?

Answer 11

Found in elasmobranchs and in freshwater teleosts
Lungfishes

Tubules divided into proximal and distal convoluted regions with large capsules

• > very dilute urine
• > secrete ammonia - ammonotelic

AMMONOTELIC

They take in and flush out a lot of water. All that excess water allows the exertion of ammonia

Question 12

What is the sttructure of the marine teleost nephron?

Answer 12

In most marine teleosts
Very small and reduced renal corpuscles allows less water to be filters and more concentrated urine
Nitrogenous waste is exerted as urea

Question 13

In the urea style nephron lots of salt is taken in but not much water is lost through the nephrons of the kidneys, they cant get rid of the salt by urine because it would be too much water loss, so how is salt eliminated in these fish? The shark?

Answer 13

In fish: gill lamellae

In shark: digitiform gland

Question 14

What type of kidney do most amniotes, including humans, have?

Answer 14

Metanephric kidney
With/ afferent and efferent arterioles, collecting duct, proximal and distal tubules. Loop of henle.

Renal corpuscles forms the base of the renal pyramids which empty into the renal pelvis and then the ureter.

Question 15

Wat is the pronephros?

Answer 15

The simplest of the three kidneys. The most primitive.

The first to develop in all vertebrates. Located near the cranial end. Non-functional in mammals. But if the pronephros dont develop neither does the rest of the kidney.

Develop from nephrotome connect to pronephros duct -> induces formation of the second kidney

Pronephros duct to be renamed mesonephric duct

Functional in: larvae of fish and amphibians and adults of primitive fish.
Transitional in vertebrate embyros
-proximal ends open into coelomic cavity. Then to the cloaca

Question 16

What is the mesanephros?

Answer 16

The main functional kidney in embryos.
Forms caudal to the pronephros.

Formation of the mesonephric duct causes the pronephros tto be nonfunctional.

Functional kidney in most adult fish and in all amphibians.
Cranial portion ^^
Glomerulus associated with mesonephric tubules are in direct contact with the renal corpuscles (direct filtration)

Grow within the pronephros duct which is renames the mesonephric duct.

Opens into the renal corpusles, not the coelom, and capillaries from the dorsal aorta.

Before the attachment to the cloaca: buds into the ureteric bud. Where the metenephric kidney forms.

Question 17

What is unique about the salamander kidney?

Answer 17

Salamanders: only caudal part of mesonephric is functional: opithonephros
“Tail kidney”

Question 18

What is the metanephros?

Answer 18

The adult kidney for most vertebrates.
Forms out of the envaginations of of the mesonephric duct called the uremic bud. (Or diverticula)

The expansion of the metanephric diverticulum causes the mesenchyme to condense into the metanephric blastmata

• which form the renal tubules
• the tubules will not form without the duct and vice versa. They need eachother to develop

The metanephric diverticulum is the part the develops into the adult kidney.

Question 19

Amphibians uriniary system

Answer 19

Primitive nephron,
Larvae: excrete ammonia - pronephros
Adult: urea - mesonephros

Well developed cloaca
Cloaca develops a urinary bladder, a mesodermal structure not like the endodermal mammalian urinary bladder.

Question 20

Urinary system of reptiles

Answer 20

renal corpuscles are reduced in living reptiles

Marine turtles have salt gland in eyes
Lizards and other turtles excrete uric acid

Crocs eliminate in the form of ammonia

Question 21

Amniotes have what sort of urinary system?

Answer 21

Larval amniotes uses the mesonephros as functional kidney and metanephros in adults

Urine conduction excluded from archinephric duct
-sperm formation

Well developed cloaca except in mammals
No urinary bladder development in birds. (Except ostrich)

Question 22

Mammals urinary system

Answer 22

Adult kidney: metanephric

Large corpulse

Loop of henle between proximal and distal consulates tubules - which creates the osmotic gradient for the water reabsorption.