Lecture 1

Question 1

List the three subphyla of the phylum Chordata

Answer 1

Cephalochordata, Urochordata, Vertebrata

Question 2

Describe the major characteristics of cephalochordates

Answer 2

Notochord located in the cranial “head”, represented by lancelets (amphioxus)

Question 3

Describe the major characteristics of urochordates

Answer 3

Represented by sea squirts (ascidians), they develop as larva with dorsal notochords, but lose them upon maturation when they reach their immobile adult phase. Body cavities are only loosely definable.

Question 4

Describe the major characteristics of vertebrates

Answer 4

Notochord develops into vertebral column - represented by the classes pisces, and tetrapods

Question 5

List the five classes grouped into the Pisces Supergroup

Answer 5

Agnatha, Acanthodii, Placodermi, Chondrichthyes, and Osteichthyes

Question 6

Describe the major characteristics of Agnatha

Answer 6

These fish lack jaws or paired appendages. Examples include the hagfish and possibly lampreys.

Question 7

Describe the major characteristics of acanthodii.

Answer 7

An extinct class which used to include spiny sharklike creatures that were possibly the first vertebrates to have jaws (gnathostomes). They share this characteristic with placoderms

Question 8

Describe the major characteristics of placoderms

Answer 8

An extinct class of gnathostomes (first jawed fish) who first developed paired fins. Ranged from very small to very large.

Question 9

Describe the major characteristics of chondrichthyes

Answer 9

Class of fish unable to form bone, but developed skeletal systems made of cartilage. Includes both extinct and extant sharks, and rays.

Question 10

Describe the major characteristics of osteichthyes

Answer 10

Largest current class of fish species, includes any fish with bone skeletal structures (though some can still retain some cartilage)

Question 11

Name the four classes of tetrapods

Answer 11

Amphibia, Reptilia, Aves, and Mammalia

Question 12

Describe the characteristics/examples of amphibia

Answer 12

Includes both extinct and extant amphibians including frogs, toads, and salamanders.

Question 13

Describe the characteristics/examples of reptilia

Answer 13

Includes extinct and extant lizards, snakes, turtles, crocodiles, and dinosaurs (including flying reptile such as pterosaurs)

Question 14

Describe the characteristics/examples of aves

Answer 14

Birds, both extinct and extant. Major characteristic is the presence of feathers.

Question 15

Describe the major characteristics/examples of mammalia

Answer 15

Extinct and extant mammals, had both hair and mammary glands

Question 16

List the four anatomical features all chordates possess

Answer 16

(Embryological) Dorsal Hollow Nerve Cord, Pharyngeal slits arches and pouches, a notochord, and a post-anal tail.

Question 17

List four features of the dorsal hollow nerve cord.

Answer 17

1. Represents future brain and spinal cord
2. Hollow tube that runs dorsal to the notochord
3. Retained as adults in vertebrates as the hollow space in brain and spinal canal
4. Can comprise of entire nervous system in some invertebrates

Question 18

Where is the pharynx located and what is the purpose of pharyngeal pouches

Answer 18

Pharynx is in Cranial portion of the gut tube. The pouches connect exterior of the organism with the interior of the pharynx, and are often retained after maturation as gill slits,

Question 19

What are pharyngeal arches and where are they found?

Answer 19

The area between pharyngeal pouches are called arches. These each contain a skeletal element, branchiomeric muscles, cranial nerves, and an aortic arch. The first arch is called the Mandibular arch (gills, auditory tubes, middle ear cavities) and the second arch is called the hyoid arch (forms the palate tonsils in mammals)

Question 20

What were the primitive original purposes of the pharynx in regard to respiration

Answer 20

Though originally for filter feeding by trapping plankton, the pharynx developed external gills from the pharyngeal pouch, which subsequently developed vascularization that allowed oxygen to be extracted from the water flowing through these gill slits.

Question 21

What is the notochord and what purpose does it serve

Answer 21

The notochord runs ventral to the nerve cord and dorsal to the gut tube and is a hollow tube made of cells resembling (but not matching) cartilage. In embryos it provides hydrostatic support in water (damage during this stage is usually devastating), but it continues to provide axial skeletal support in agnathans.

Question 22

In mammals, what becomes of the notochord post-embryologically?

Answer 22

Notochord breaks down and forms intervertebral disc nucleus. Also initiates the formation of the central nervous system (brain).

Question 23

Describe the vertebral column

Answer 23

Only In vertebrates, the vertebral column is a series of irregularly shaped elements (cartilage and/or bone) that protect the nerve cord and provide axial support. Land animals rely on it since it’s more rigid and resistant to gravity, though fish still retain some notochord elements due to flexibility required underwater.

Question 24

What are the three general “sections” of the vertebrate body, and what characteristics do they have?

Answer 24

1. Head - Cephalization - usually the location of sensory organs
2. Body - Contains viscera and central support for the appendages. Can also consist of a slender stalk connecting the head (the neck)
3. Tail - Begins at the caudal opening of the digestive tract - the anus. Often lost post-embryologically or after a certain level of maturation. Can be used for defense/swimming/support/etc…

Question 25

List the eight characteristics vertebrates share with invertebrates

Answer 25

1. Cephalization 2. Complete Digestive Tract
2. Bilateral Symmetry 4. Metamerism (segments with distinct function?) 5. Triploblasty 6. Eucoelomate body Cavity
3. Closed circulatory system 8. Deuterostomy

Question 26

List the 8 directional terms associated with anatomy and their 4 correlated axes

Answer 26

Proximal/Distal, Ventral/Dorsal, Left/Right, Anterior/Posterior

Proximodistal Axis, Dorsoventral Axis, Left/Right Axis, Anteroposterior Axis

Question 27

Name the 3 axes commonly used with quadripedal organisms

Answer 27

Cranial/Caudal (Vertical Axis - Usually parallel to the spine)
Dorsal/Ventral Axis (Saggital, or anterior posterior axis - perpendicular to the spine)
Left/Right Lateral Axis

Question 28

Define the 3 planes of symmetry and which 2 axes run together to create it.

Answer 28

Saggital - Cranial/Caudal intersects with Anterior/Posterior
Frontal (Coronal) - Cranial/Caudal intersects with Left/Right
Transverse (Cross-Section) - Dorsal/Ventral intersects with Left/Right

Question 29

List the five movements of bilateral symmetry

Answer 29

Flexion, Extension, Abduction, Adduction, Rotation

Question 30

Describe the movements for Flexion and Extension

Answer 30

Flexion - Bending movement that takes place in a saggital plane around the left/right axis. Usually brings two body parts closer together. The fetus is developed in a fully flexed position
Extension - Straightens out a bent joint in the same saggital plane around the left/right axis

Question 31

Describe the movements for abduction, adduction, and rotation

Answer 31

Abduction - Away from the midline, such as raising arms to the side, or extending fingers
Adduction - A reversal of Abduction, where body parts are directed towards the midline. (Bringing arms back to waist)
Rotation - Movement of the body Around the caudal plane in a transverse plane

Question 32

The vertebrate body plan is generally thought to be comprised into Two distinct tubes. Describe the outer tube.

Answer 32

The somatic tube is what interacts with the external environment and consists of both skin, and skeletal muscle. It is intended to detect changes in the external environment and appropriately respond.

Question 33

The vertebrate body is thought to be comprised into two distinct tubes. Describe the Inner Tube

Answer 33

The splanchnic, or visceral tube is generally thought to be for metabolism. It involves the gut tube (alimentary tract) and derivitives, such as the liver and pancreas.

Question 34

In the animal kingdom, the somatic tube and the splanchnic tube are separated by an internal space called the coelom. List and describe the 3 types an organism can have based on their coelum.

Answer 34

• Acoelomates lack a body cavity separating the somatic tube from the visceral tube
• Pseudocoelomates possess a cavity, but it is only partly derived from embryonic mesoderm.
• Eucoelomates includes most animals and chordates; they possess a body cavity that is completely in line with derivatives of embryonic mesoderm.

Question 35

There are 2 mesodermal derivatives within the coelom of eucoelomates. Name them and their location.

Describe mesenteries.

Answer 35

• The lining associated with the somatic tube is referred to as somatic or parietal peritoneum (or pleura or pericardium).
• The lining that is intimately associated with the splanchnic tube is referred to as visceral peritoneum (or pleura or pericardium).
• Places where these two linings meet form double-layered suspensory structures called mesenteries, which help supply pathways for blood vessels to reach to reach visceral organs. (See slide 41 in lecture 1)

Question 36

Name 8 other characteristics that vertebrates often share with non-vertebrates.

Answer 36

1. Paired Appendages, 2. Internal mesodermal skeleton,
2. Epaxial/Hypaxial Musculature, 4. Subdivided Coelom,
3. Segmentation/metamerism, 6. Triploblasty,
4. Deuterostomy, 8. Cephalization

Question 37

Describe Paired Appendages and their types

Answer 37

• All modern vertebrates have paired appendages, though some are lost secondarily or modified.
  Classified into two categories: Pectoral Appendages, and Pelvic Appendages. Both of which have similar anatomical patterns.

Question 38

Describe the internal mesodermal skeleton

Answer 38

All vertebrates have an internal mesodermal layer, which forms the mesoderm, one of the three embryonic germ layers. The mesoderm gives rise to many internal structures, including the skeletal system, be that cartilage or bone. (Cartilage often develops into bone embryologically)

Question 39

Describe the layout of hypaxial and epaxial muscles and which human muscles consist of each.

Answer 39

Epaxial Musculature - lies above the dorsal ribcage and is shaped in block-like structures called myomeres. Useful in fish for locomotion. Not as common of a feature in humans.
Hypaxial Musculature - Often found below the dorsal ribs and lateral to the ventral ribs, this type of musculature is more layered as is the common component of skeletal muscle in the walls of body cavities, and limbs.

Question 40

The coelom is divided into two different mesodermal subdivisions in most vertebrates, but three in mammals. Name them, and describe what is housed in each

Answer 40

Vertebrates: (Pericardial - heart), (Pleuroperitoneal - lungs, and other viscera)
Mammals: (Pericardial - Heart), (Pleural - Paired cavities of Lungs), (Peritoneal - other viscera)

Question 41

Describe what separates the subdivisions of the pericardial and pleuroperitoneal cavities in fish, amphibians, reptiles, birds, and mammals.

Answer 41

Transverse Septum (Fibrous wall separates cavities in fish, amphibians, and some reptiles)
Tendinous Oblique Septum (Separates cavities in other reptiles, and birds)
Muscular Diaphragm - Partitions off pleural cavities in mammals

Question 42

What is the name of the collective mesodermal linings and what sort of properties do they have

Answer 42

The mesodermal linings are collectively referred to as the serous membrane, which produces a thin watery lubricating fluid.

• These layers are known as the Parietal Layers, such as Parietal Pleura, Parietal Pericardium, etc…
• There are also membranes covering the organs within the body cavities called visceral membranes. (Eg. Visceral Pericardium, Visceral Peritoneum, etc…)

Question 43

Describe Mesenteries

Answer 43

The transitional points where the visceral and parietal peritoneum membranes form are called mesenteries. There are 2 main mesenteries: The Dorsal Mesentery connects the dorsal roof to the gut tube, and the Ventral Messentary connects the gut tube to the ventral floor.

Question 44

• Describe where VM-2 is found.
• Describe where VM-1 is found.
• What is the fate of the ventral mesentery, when, and why?
• What are the organs outside the peritoneum referred to and what’s an example?

Answer 44

• In the cranial part of the peritoneal coelom, the ventral mesentery connecting the liver to the floor of the peritoneal cavity forms the falciform ligament (VM-2).
• The part of the ventral mesentery between the liver and the ventral gut tube is the lesser omentum (VM-1).
• Most of the rest of the ventral mesentery is obliterated during embryonic development due to the elongation and coiling of the gut tube.
• Some organs such as the kidneys lie behind the peritoneum and are referred to as retroperitoneal.
• Take note of the diagram on slide 50

Question 45

Describe metamerism

Answer 45

• Metamerism refers to segmentation and describes the subdivision of the body into repeating anatomical units on either side of the midline extending from the cranial to the caudal end.
• Metamerism is easy to observe in many invertebrates such as earthworms and insects, but it is also very evident in vertebrates, although not so obvious externally.
• The epaxial musculature is divided into repeating blocks of skeletal muscle (myomeres) lying on either side of the notochord or vertebral column. This is especially evident in fish but can also be seen in tetrapods.
• Metamerism is also evident in the anatomy of the vertebral column, nervous system and kidneys.

Question 46

List the three germ layers resulting from triploblasty and give an example of the organs found in each layer

Answer 46

Ectoderm - outermost germ layer, and holds the nervous system, and the integument (skin).
Mesoderm - Middle Germ Layer; Holds connective tissue, bones, cartilage, muscle, and other similar structures.
Endoderm - Inner Germ Layer; Houses the Gut tube, and derivatives.

Question 47

Describe deuterostomy

Answer 47

• NOT unique to chordates
• Refers to the origin of the oral opening in relation to the anal opening during embryonic development.
• In deuterostomes, the original embryonic opening (the blastopore) becomes the anus, and the mouth develops as a secondary opening.

Question 48

Describe cephalization

Answer 48

• NOT unique to chordates

- Refers to the development of a definite head (cranial end) characterized by an accumulation of sense organs

Question 49

What are some other characteristics of vertebrates that are not necessarily unique or exclusive?

Answer 49

• Vertebrate body is divided into three regions, which is characteristic of vertebrates.
• The head with it’s concentration of sense organs is generally the first part of the vertebrate body to enter a new milieu.
• The trunk contains most of the viscera and serves as the central support for the appendages.
• The tail begins at the caudal opening of the digestive tube (the anus) and is the main organ of locomotion in many fishes, salamanders, and tadpoles. Some vertebrates lose the tail in the adult form (frogs, primates, and birds).