Comparative Anatomy Exam 3

This is a knowt for exam 3 (lectures 9-12) going off of Dr. Armbruster's review and from the text book, make sure that you review diagrams and phylogenetic trees.

What is the digestive tract?

A tubular passageway that extends from the lips of the mouth to the anus or cloacal opening.

What is the buccal cavity?

The teeth, tongue, palate, and oral glands.

Mammals have what kind of cells in their Fundic Glands?

Chief and Parietal Cells

What do the Parietal Cells produce?

HCl

What do the Chief Cells produce?

Pepsinogen

What are Oxyntopeptic Cells and who has them?

HCl and Pepsinogen, and everyone except mammals has these cells. Mammals split up the cells into Chief and Parietal cells.

What is a function of HCl?

It cleaves pepsinogen (weak proteolytic enzyme) into pepsin (strong proteolytic enzyme).

What does Microvilli do?

Increase absorptive area and provides a beneficial microenvironment to enzymes.

What are foregut fermenters?

Foregut fermenters use their stomachs and/or their esophagus to break down food. (Kangaroos, Camels, Hoatzin)

What are hindgut fermenters?

Hindgut fermenters use the cecum to break down their food.(Horses, rabbits, pigs, koalas, many amphibians, reptiles, and birds)

Ruminants (name the type of fermenter, how many stomach chambers, and animal examples)

• Foregut Fermenters

• 4-chambered stomach

• Deer, Giraffes, Cows

What are the 4 parts of a Ruminants stomach?

Rumen, Reticulum, Omasum, Abomasum (true stomach)

What is the order in which food goes through a ruminants stomach?

Esophagus —> Rumen—> Reticulum—> Omasum—> Abomasum—> Intestine

What does the Reticulum do?

The food is moved around and forms cud, which will be re-masticated and then re-swallowed. It may go back to the rumen or go to the Omasum.

What does the Omasum do?

The omasum will sieve and compact the cud further. Can be repeated or go to the abomasum.

What does the Rumen do?

The rumen is the fermentation tank, food comes down and the bacteria in the rumen breaks down the starches into sugars before it goes to the reticulum.

What does the Abomasum do?

This is the true stomach, from here food goes to the intestines.

What is a problem with being a hindgut fermenter?

Proteins produced from fermentation can’t be absorbed (coprophagy to compensate)

What starts digestion in mammals?

Oral glands (amylase)

What is responsible for forming the buccal cavity and contributes to the surface features of the head in some vertebrates?

Stomodeum

What part of the head invaginates in lamprey?

Only the posterior part of the stomodeum, contributing to the mouth. The anterior part turns outward, contributing to the outer surface of the head.

What are the two anterior parts of the stomodeum?

Hypophyseal Pouch and Nasal Placode

What do the hypophyseal pouch and the nasal placode combine into in Lamprey?

They combine to form the nasohypophyseal canal

How does the stomodeum invaginate in Chondrichthyes and Bony Fishes?

Slightly further than lamprey, the hypophyseal canal stays inside the mouth while the nasal placode remains on the outside of the head.

How does the stomodeum invaginate in Osteolepimorphs and Tetrapods?

The stomodeum invaginates further, bringing the nasal placode into the mouth as well as the hypophyseal canal.

What is the pharynx?

In adults, the pharynx is little more than a corridor for the passage of food and air.

What does the pharynx form from?

From the anterior foregut (endoderm)

What are pharyngeal pouches?

A series of bays that form on the lateral walls of the throat region of developing embryos.

The pharyngeal pouches meet in-pocketings of ectoderm, called what?

Branchial grooves

At the point of contact, the branchial grooves and pharyngeal pockets form what?

Closing plates

What happens to the closing plate in fishes?

They perforate to form gills

What is the Square-Cube Law?

When the size of a structure is doubled, the surface area increases by the square (2X2 = 4x) and the volume by the cube (2X2X2 = 8x).
Double the size of the organism, mass increases by 8x

What is the gingiva of a tooth?

The gum line

What is the area above the gingiva?

The crown

What is the area below the gingiva?

The base, or root if it’s in the socket

What is the pulp/pulp cavity?

The mucous connective tissue (the black shape)

What is the enamel?

The hard outside of the tooth

What is dentin?

The inside underneath the enamel and cementum, forms the walls of the pulp cavity.

What is cementum?

Cementum rests upon the dentin and grows in layers on the surface of the roots.

What is the periodontal ligament?

The periodontal ligament consists of thick bundles of collagenous fibers that connect the cementum-covered root to the bone of the socket.

What are homodont teeth? (think of dolphin teeth)

Homodont teeth are all similar in appearance throughout the mouth

What are heterodont teeth? (think of cats teeth

Heterodont teeth are teeth that differ in appearance throughout the mouth.

What is polyphyodont? (sharks)

Many sets of teeth, teeth are continuously replaced

What is diphyodont? (most mammals, including us)

Two sets of teeth throughout entire lifetime

What are the first set of diphyodont teeth called?

Deciduous dentition (baby/milk teeth)

What are the second set of diphyodont teeth called?

Permanent dentition

What is thecodont tooth attachment? Who has them?

Teeth are attached into the socket. (Mammals, crocs, dinos)

What is acrodont tooth attachment? Who has them?

Teeth are attached to shallow sockets at the crest of the bone (most fishes and snakes)

What is pleurodont teeth attachment? Who has them?

Teeth are connected on the medial side of the jaw. (Lizards)

What are brachydont teeth? Who has them?

Brachydont teeth have low crowns (humans, pigs; omnivores, carnivores)

What are hypsodont teeth? Who has them?

In hypsodont teeth, the crowns are high. (Horses, cows; herbivores)

What are bunodont teeth? Who has them?

Bunodont teeth are a brachydont tooth that have rounded cusps (Humans, pigs; omnivores, carnivores)

What are lophodont teeth? Who has them?

Lophodont teeth are hypsodont teeth with cusps that are drawn into ridges. (Perissodactyls—horses, rodents, elephants)

What are selenodont teeth? Who has them?

Selenodont teeth are hypsodont teeth that have crescent-shaped cusps (Artiodactyls: cows and deer)

What is ammonotelism?

The direct excretion of ammonia.

What is uricotelism?

Excretion of nitrogen in the form of uric acid.

What is ureotelism?

The excretion of nitrogen in the form of urea.

How do hagfishes and other fish excrete ammonia?

They use ammonotelism.

How do mammals excrete ammonia?

They depend on ureotelism.

How do birds and most reptiles excrete ammonia?

They depend on uricotelism.

How does a kidney develop?

The nephric ridge forms from either side of the midline. The nephric ridge breaks up into nephrotomes, which are often segmented and contain nephrocoel. The nephrocoel is often connected to the coelom via a ciliated peritoneal funnel. Next, the medial end of the nephrotome widens into a thin-walled renal capsule, into which grows the glomerulus. The lateral end of the nephrotomes grows outwards to form the nephric duct. From here, the nephrotomes become the uriniferous tubules.

What are the three regions of nephric tubules in the kidneys?

Pronephros, Mesonephros, Metanephros

Describe the development of the Pronephros

Tubules form anteriorly first, and the tubules combine to form the pronephric duct (at 3 weeks in humans). This duct grows posteriorly in the nephric ridge, eventually reaching and opening into the cloaca, and often retains connection to coelom.

Describe the development of the Mesonephros

Tubules of the mesonephric kidney form in the middle of the nephric ridge (3.5 weeks). It opens into the pronephric duct, now called the mesonephric duct. Once the mesonephros forms, the pronephros regresses. The mesonephros is present and active in all embryos, and in adults, tubules are added in the posterior kidney called the opisthonephros.

What animal only has the mesonephros by itself?

Hagfish

Describe the development of the Metanephros

The ureteric diverticulum forms at the base of the mesonephric duct (5 weeks) and stimulates the development of tubules in the metanephros. Once this happens, the mesonephric duct takes on other functions (Males: vas deferens; Females: goes away). The ureteric diverticulum then connects to the urinary bladder, forming the ureter.

What is the Holonephros?

The holonephros comes from the holonephric concept, which says that the nephric ridge is one continuous, complete organ.

What type of kidneys do Hagfish (Juveniles vs. Adults) have?

Juveniles have just the pronephros with no glomeruli anteriorly but still connected to the coelom.

Adults retain the pronephros but not as a kidney. It makes coelomic fluid. The adult kidney is just in the mesonephros.

What type of kidneys do Lampreys (Larva vs. Adult) have?

Larva have pronephros with 8 tubules serviced by glomus.

Adults have tubules in both the meso and metanephric regions.

What type of kidneys do other fishes have?

The pronephros develops but usually regresses when the mesonephros forms.

The adults have opisthonephros. The pronephros is retained as an immune or hematopoietic organ in some. The pronephros is also used in some species as a functional kidney, particularly in some progenic species

What kind of kidney do Amphibians (Larva vs. Adult) have?

In larvae, the pronephros is usually functional.

Adults have opisthonephros.

What kind of kidney do Amniotes have?

Pronephros rarely produces nephrons, which never produces urine. Loops of Henle are present.

Nephron structure relates to what?

Osmoregulation

What are osmoconformers?

They are isosmotic, or the same ion concentration as seawater. Seen in hagfishes, chondrichthyes, and coelacanths.

What are osmoregulators?

They are hyperosmotic or hyposmotic.

What does hyperosmotic mean?

Body is saltier than the surrounding water. They take in water and release salts. Uptake of salts through chloride cells in the gills.

What does hyposmotic mean?

Body is less salty than the surrounding water. Salt is taken in and water is released. Chloride cells in gills actively pump out salts.

How do tetrapods osmoregulate?

Water evaporates from tissues and takes salts along with it, so both need to be conserved. Uri acid and loops of Henle conserve water. Salt is eliminated through GI tract or nose.

How does the hagfish and lamprey male anatomy work?

Sperm sheds into the coelom and exits via abdominal pores. Archinephric ducts drain the kidneys.

How does male elasmobranch anatomy work?

Reproductive kidney with short tubules connecting the testis to the archinephric duct. The archinephric duct is only for sperm.

How do male bony fishes anatomy work?

The archinephric duct may receive urine and sperm. Some species lack a duct and release sperm into coleom

How do salamanders copulate?

Males produce spermatophores and the females pick them up.

What type of intromittent organ do sharks have?

Claspers

What pumps sperm down the grooves in the pelvic fins of sharks?

Siphon

What type of intromittent organs do many teleosts use? (Guppies)

Gonopodium

What type of intromittent organs do amniotes have?

Generally have a penis, but not homologous across groups

What type of intromittent organ do tuataras, snakes, and lizards have?

Hemipenes

Bifurcated penises are found in what mammals?

Monotremes and Marsupials

Name for penis bone present in most mammals

Baculum

What is the female homolog to the baculum?

Baubellum or clitoris

In the female reproductive system, what produces eggs?

Ovary

What delivers the eggs to the oviduct?

Ostium

What holds the eggs prior to laying or young?

Uterus

Hagfish and Lamprey have how many ovaries?

Single large ovary suspended middorsally

Describe Tetrapod female reproductive systems

Ovaries are usually paired, and the new metanephric duct is the ureter. The archinephric duct regresses. Oviducts may have prominent sheets of smooth muscles.

What is the uterus?

Terminal portion of oviduct, holds shelled eggs or embryos. Associated with the placenta.

Describe Monotreme uteruses

No vagina or cervix, duplex uterus. Urogenital sinus— urethra and uteri combine.

Describe Metatherian uteruses

Duplex uterus, two vaginas and two cervices. Some with vaginal sinus.

What kind of uterus/birth canal do kangaroos have?

Median birth canals

What kind of uterus do rodents and rabbits have?

Duplex uterus with two horns and cervices, and urogenital sinus— urethra and vagina combine