Term
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Definition
-Not present in nonvertebrate chordates
-The “teeth” of cyclostomes are keratinized epithelial structures (not homologous with the teeth of the other vertebrates)
-Present in the other vertebrate taxa; secondarily lost in a few groups, including:
-Fishes: sturgeons, sea horses
-Amphibians: some anurans
-Reptiles: all turtles
-Birds: all modern birds (Archaeopteryx had teeth)
-Mammals: baleen whales, some anteaters, and the Echidna (a monotreme). |
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Term
Teeth Evolutionary Origin |
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Definition
-Derivatives of dermal bony plates at the margins of the mouth (Reminder: bony plates were made of layers of an enameloid over dentin over bone) -Teeth developed almost simultaneously with the jaws. |
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Term
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Definition
-Inner space is the pulp cavity; filled with soft tissue, nerves and blood vessels.
- The tooth is embedded into the tissue of the jaw bone (gums or gingiva) by its base (if the base is in a socket, it is called a root).
-Nerves and blood vessels pass from the gums into the pulp cavity through a narrow root canal.
- A layer of dentine (a substance that is chemically similar to bone) surrounds the pulp cavity. It is laid down slowly throughout the life of the animal.
-Teeth are attached to the jaw bone by a spongy bone-like substance called cementum. The amount increases irregularly with age.
-The crown or exposed portion of the tooth is covered with enamel, a very hard bone-like substance. For most animals, enamel does not continue to be deposited after the tooth erupts. |
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Term
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Definition
-Embryological development is from both the dermis (mesoderm) and epidermis (ectoderm).
-They initially develop within the dermis.
-The epidermis produces the enamel organ, which produces cells called ameloblasts that secrete enamel
-Mesenchymal cells of neural crest origin gather in the dermis, producing the dermal papilla which produces cells called odontoblasts that secrete dentine.
-Tooth development parallels the development of placoid scales. Shark teeth are simple modifications of placoid scales. |
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Term
Teeth Attachment to the Jaw Bone |
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Definition
-Arcodont dentition: Teeth are attached to the outer surface or to the summit of the jaw bone (typical of most teleost fishes and snakes) -Pleurodont dentition Teeth are attached to the inner surface of the jaw bone (typical of amphibians and lizards) -Thecodont dentition: Teeth are implanted into deep sockets (typical of some fishes, crocodilians, extinct toothed birds, mammals). Multiple roots are generally confined to the cheek teeth of mammals. |
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Term
Teeth Shape and Permanence |
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Definition
Fishes, Amphibians, Reptiles
- Homodont: teeth have similar shape throughout the mouth.
- Polyphyodont: replaced continuously
Mammals
- Heterodont: differing in shape throughout the mouth.
- Diphyodont (characteristic of most mammals): develop 2 sets of teeth, deciduous (1st) and permanent (2nd). As the permanent tooth grows against the root of the deciduous tooth, nutrition to the deciduous tooth is cut off; the root is resorbed and the crown is lost.
- Monophyodont dentition (characteristic of a few mammals; e.g., some rodents, some whales, seals, manatees): only one set of teeth. |
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Term
Heterodont Teeth of Mammals: Incisors |
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Definition
located on either side of the mandibular symphysis; usually have a horizontal cutting edge and a single root. Most tusks are incisors that grow continuously (e.g., tusks of elephants, mastodons, narwhales). The incisors of rodents also grow continuously. |
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Term
Heterodont Teeth of Mammals: Canines |
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Definition
Lie next to the incisors; may be similar in appearance to the incisors, or, particularly in carnivores, may be spear-like for piercing flesh. When canines or incisors are missing, the “bare” bone is called the diastema (e.g., rabbits, ox, mule deer; see Fig. 13.14). Walrus tusks are canines that grow continuously. |
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Term
Heterodont Teeth of Mammals: Premolars |
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Definition
located behind the canines; most have two cusps on the crown (“bicuspid” teeth) and may have one or two roots, depending on the individual. |
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Term
Heterodont Teeth of Mammals: Molars |
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Definition
located behind the premolars; most have three (or more) cusps on the crown (“tricuspid” teeth) and usually three roots. In diphyodonts, molars are not replaced (they arrive late but are actually part of the first “set”). In elephants and manatees, molar teeth erupt sequentially over a protracted period; a new molar erupts at the back of the tooth row and pushes older molars to the front. |
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Term
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Definition
A) Brachyodont molars have crowns that are relatively low (Fig. 13.15a); e.g., humans, pigs.
B) Hypsodont molars have crowns that are relatively high (Fig. 13.15b); e.g., horses |
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Term
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Definition
A) Bunodont molars have cusps that form peaks (Fig. 13.15c); e.g., omnivores
B) Lophodont molars have cusps drawn out into ridges (Fig. 13.15d; e.g., rodents, horses
C) Selenodont molar have cusps that are crescent shaped (Fig. 13.15e); e.g., camels, cattle, deer
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Term
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Definition
- Innermost layer
- Anterior: typically contains a variety of secretory cells that produce mucous, enzymes or other substances that aid in digestion.
- Posteriorly: functions primarily in absorption.
- Sub-layers:
->Surface layer: epithelium
->Middle layer: lamina propria composed of loose connective tissue containing blood vessels
->Basal layer: smooth muscle called the muscularis mucosae; controls movement of the gut lining (independent of the movements of the tube as a whole)
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Term
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Definition
- Surrounds the mucosa - Loose connective tissue containing nerves, capillaries, and lymph vessels |
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Term
The Gut: Muscularis Externa |
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Definition
(smooth muscle surrounding the submucosa);
contains two layers whose coordinated action accomplishes peristalsis:
- Circular layer
-> Fibers arranged in a spiral around the gut
-> Contractions lengthen the gut and decreases its diameter
- Longitudinal layer
-> Fibers arranged lengthwise on the gut
-> Contraction shortens the gut and increases its diameter |
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Term
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Definition
- Surrounds the muscularis externa - Composed of epithelial tissue underlain by connective tissue |
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Term
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Definition
Esophagus and Stomach — passageway (plus some digestion) |
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Term
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Definition
short esophagus which has papillae or folds directing food toward the stomach. The stomach is straight or bent like a "J" or "U" |
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Term
General tetrapods Foregut |
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Definition
The stomach is subdivided into regions based on the type of epithelium lining the mucosa: (fig. 13.31)
- Cardiac (only found in some birds and mammals): contains many mucous glands
- Fundus: contains glands that produce mucous, digestive enzymes (primarily pepsin for protein break-down and a lipase that breaks down fats), and hydrochloric acid (which lowers the pH)
- Pylorus: attaches to the small intestine; contains mucous glands
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Term
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Definition
-A long esophagus with a keratinized lining
-Lower portion of the esophagus may be dilated to form a storage organ (crop)
-Subdivisions of stomach:
-> The anterior fundus or proventricularis: glandular; produces digestive enzymes
-> Ventricularis, or gizzard: very muscular for the grinding of food
-> The pylorus: secretes mucous |
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Term
Even-toed ungulates Foregut (aka Artiodactyls or “ruminants”) |
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Definition
-Food first passes into the Rumen of the esophagus where it is pulverized by muscle action and fermented by bacteria and protozoans to break down cellulose (these microorganisms also produce vitamins, amino acids, and fatty acids)
-The “cud” is regurgitated for further chewing
-After the second swallowing, the food passes directly into the reticulum and omasum compartments of the esophagus where additional break-down occurs.
-Finally, the food passes into the abomasum which contains cardiac, fundic and pyloric epithelium. This portion acts like a “true” stomach.
-Other foregut fermenters: manatees, kangaroos, langurs, sloths and one bird, the hoatzin |
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Term
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Definition
-Intestines
-most digestion (chemical break-down) and absorption
-Separated from the stomach by a pyloric sphincter |
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Term
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Definition
A single straight or curved tube with (no “small/large” subdivisions) Adaptations to increase surface area and slow passage of food Hagfishes, elasmobranchs, and lungfishes: intestine ends in a chamber called the cloaca, which also receives ducts from the excretory and reproductive systems Lampreys and most bony fishes: intestine ends in a chamber called the rectum that is separate from renal and genital ducts, although the three may share a common opening.
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Term
Tetrapods anterior Hindgut |
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Definition
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Term
| Tetrapods posterior Hindgut |
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Definition
the colon
-shorter than the small intestine and relatively straight
-In mammals, the colon has a very large diameter and is shaped like a “?” or an inverted"U"
-It is separated from the small intestine by an ileocolic valve.
-Most important function is the resorption of water
-Bacteria break down some of the remaining food materials. |
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Term
Some specializations of the Hindgut |
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Definition
Adaptations to increase surface area and/or slow passage of food
- Primitive fishes and elasmobranchs: a spiral valve runs down the length of the lumen of the intestine.
-Modern Fishes: Cecae near the pyloric sphincter
-Mammals: Mucosa of small intestine is covered with finger-like projections called villi (fig. 13.25)
-Villi are made up of more finger-like projections called microvilli
-Mammals: One or more cecae at the juncture of the small and large intestine (cecae terminate in the vermiform appendix in primates)
-Mammals: Small intestine is long slender and, usually, highly coiled |
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Term
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Definition
(long large intestines and large cecae): pigs, horses, rabbits and koalas. (Fig. 13.34b; Fig. 13.45b) Amphibians, reptiles, birds, and monotreme mammals have a cloaca Placental mammals have a rectum that exits at an opening (the anus) that is separate from that of the renal and genital ducts
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Term
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Definition
-Two ventral out-pockets develop from the gut tube just posterior to the stomach (Fig. 13.38d) -> Anterior-most: becomes the liver. -> Posterior-most: becomes the gall bladder. -Lobes: The number and position of the lobes of the liver are variable and apparently have little systematic significance. |
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Term
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Definition
-> Storage of carbohydrates (via conversion of glucose to glycogen) and fats -> Conversion of proteins to carbohydrates or fats (nitrogenous wastes go to the kidneys). -> Removal of "old" red blood cells from circulation (bile pigments are derived from the hemoglobin of Red Blood Cells). -> Removal of toxicants from the blood. -> Release of clotting factors. -> Secretion of bile to the duodenum for fat emulsification. |
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Term
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Definition
-> Bile from the liver is drained via the hepatic duct. -> If there is no food in the small intestine, bile "backs up" into the gall bladder (where it is stored) via the cystic duct. -> The cystic and hepatic ducts merge, forming the common bile duct before entering the duodenum |
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Term
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Definition
-Embryology: Develops as a dorsal out-pocket from the gut at the level of the liver
-Structure: Ranges from diffuse tissue in fishes to more compact tissue, sometimes with lobes (tetrapods).
-Ducts: Single or multiple pancreatic ducts may be present; they empty into the duodenum either directly or via the common bile duct.
-Functions:
-> Exocrine (secretion into ducts): production of enzymes for digestion by acinous cells.
-> Endocrine (secretion into the blood): secretion of the hormones insulin and glucagon for control of the intermediate metabolism of carbohydrates (which occurs in the liver); the endocrine cells in the pancreas are the Islets ofLangerhans. |
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Term
Excretory organs and functions |
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Definition
-Kidney, urinary bladder and associated tubules. -Functions: -> Removal of nitrogenous waste products and other toxins. -> Elimination of water and salts (maintenance of homeostasis or a steady-state). |
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Term
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Definition
-> Develops from the Mesomere (mesoderm) -> The mesomere pinches off from the epimere and extends the length of the coelom. -> Anteriorly, the mesomere becomes segmented into units called nephrotomes. -> Posteriorly, the mesomere is unsegmented and forms a nephric ridge. |
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Term
Excretory organs: Taxonomic diversity |
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Definition
The mesomere becomes subdivided as development proceeds in sequence from anterior to posterior. The more anterior regions usually degenerate as the posterior regions become functional. |
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Term
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Definition
• Arises first during development • Most anterior region • Tubules produce a Pronephric Duct that empties into the cloaca • Functional in early tetrapod embryos and in larval bony fishes/amphibians • Usually disappears as development proceeds. |
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Term
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Definition
• Tubules arise in the middle of the nephric ridge • Tubules tap into the existing pronephric duct (now called the mesonephric duct) • Functional in amniote embryos, then disappears (see below for fishes/amphibians) |
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Term
The Opisthonephros and The Metanephros |
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Definition
-> The Opisthonephros
• The mesonephros plus some posterior tubules (“opisth” = behind)
• Functional in adult fishes and amphibians
-> The Metanephros
• Most posterior region
• Forms a new duct, the metanephric duct which will become the ureters.
• Functional kidney of adult amniotes
• What happens to the mesonephric ducts?
- Males: function in sperm transfer and are called the vas deferens.
- Females: they degenerate
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Term
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Definition
Nitrogen is excreted as one of three compounds -> Ammonia: Very toxic; requires lots of water for dilution. Typical of fishes -> Uric Acid: Moderately toxic; forms a precipitate with other molecules and requires very little water (semi-solid). Typical of reptiles and birds -> Urea: Moderately toxic: concentrated and secreted as urine. Typical of amphibians and mammals |
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Term
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Definition
outpockets of either the mesonephric ducts (fishes) or the embryonic cloaca (tetrapods) |
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Term
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Definition
-Main structures are the gonads (ovaries and testes) for production of the gametes (eggs and sperm), gonadal tubes and ducts, and accessory structures for the transport of gametes and protection and nourishment of the young.
-Sources for the development of the gonads:
-> Gonad body: develops from the mesomere (mesoderm): genital ridges develop after the mesonephros is established
-> Germ cells (gametes): migrate to the gonad from the endoderm of the primitive streak
-Ovaries and testes develop identically initially (indifferent stage)
-The gonad is two layers
-> Outer layer: Cortex
-> Inner layer: Medulla |
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Term
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Definition
-> Ovary:
- The cortex is the predominant layer with:
• oogonia: precursors to ova
• follicle cells: nourish and support the ripening eggs.
• theca: envelopes that enclose the follicles
- The medulla is a matrix of connective tissue and vessels
- Usually paired, but sometimes there is only one (e.g., in most birds)
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Term
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Definition
-> Testes
- The medulla is the predominant layer (cortex is only a thin covering)
- Cords within the medulla become hollow, producing either:
• Seminiferous tubules: germ cells are in various stages of maturation (amniotes)
• Seminiferous ampullae (sac-like): germ cells all mature together; ampulla collapses after sperm are released. (agnathans and salamanders)
- Usually located within the abdominal cavity; in some mammals descend into external coelomic pouches (scrotum) |
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Term
Female Reproductive Tract |
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Definition
-> Embryology: - a new duct called the Müllerian duct arises that develops into the oviduct, uterus and vagina (when present) - the mesonephric duct (aka the Wolffian duct) regresses -> Taxonomic diversity - Cyclostomes: lack ducts; eggs are shed into the coelom and pass into the cloaca through pores. - Teleost (modern) fishes: the Müllerian duct regresses and a new ovarian duct directly connects to the ovary. (Fig.14.24) - All others: the genital duct (Müllerian duct) does not directly attach to the ovary. |
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Term
Male Reproductive Tract Taxonomic diversity |
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Definition
- Cyclostomes: Unpaired testes with no ducts; Sperm are shed into the coelom and enter the cloaca through abdominal pores - All others: Typically, the mesonephric duct (aka vas deferens) transports sperm (fig. 14.35 c, d) |
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Term
Male Reproductive Tract fishes and amphibians Copulatory organs |
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Definition
- Fishes: Typically, none (fertilization is external). Exceptions:
(A) Shark claspers: insert into the female’s cloaca. Sperm leave the males cloaca and run through a grove on the clasper
(B) Gonopodium: in some fish (like guppies) the anal fin is modified into a grooved intromittent organ for sperm transfer
- Amphibians: Typically, none:
(A) Frogs typically have external fertilization
(B) Male salamanders produce packets of sperm called spermatophores that females pick up into their cloacae (some can store the sperm for months)
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Term
Male Reproductive Tract birds, reptiles, and mammals Copulatory organs |
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Definition
- Reptiles: Paired intromittent organs called a hemipenes (stored inside the body) - Birds: Typically none; fertilization is internal, sperm is transferred by pressing the cloacae together. Ostriches have a true penis with an erectile shaft. - Mammals: all copulate with a penis; many have a bone called a baculum in the penis. |
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