Chordate Development and Anatomy

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Questions and Answers

What is the primary function of pharyngeal slits in chordates?

Respiration and feeding (correct)

Locomotion

Reproduction

Sensory perception

Which structures are involved in the formation of the postanal tail?

Notochord and muscles only

Ectoderm only

Endoderm only

Mesoderm and ectoderm (correct)

What role does the endostyle play in filter feeding?

Facilitates gas exchange

Aids in food capture through mucus (correct)

Serves as a muscle attachment site

Produces hormones

Which of the following is NOT one of the canonical five characters shared by all chordates during some stage of development?

Digestive tract Signup and view all the answers

What is meant by 'ontogeny' in biology?

The developmental history of an individual Signup and view all the answers

What observation can be made about the morphology of some chordates during development?

Some characters are visible only in embryonic stages. Signup and view all the answers

During what stage does cleavage occur in early development?

Zygote stage Signup and view all the answers

Which factor contributes to the evolutionary signal in the development of organisms?

Conserved developmental processes and genes Signup and view all the answers

What role do Hox genes play in development?

They help in antero-posterior patterning. Signup and view all the answers

What happens when thoracic mesodermal tissue is transplanted into the neck region of an embryo?

Vertebrae form with thoracic characteristics. Signup and view all the answers

What is the primary function of the notochord during neurulation?

It induces the formation of the neurectoderm. Signup and view all the answers

What type of skeleton is characterized by bone preformed in cartilage?

Endoskeleton Signup and view all the answers

Which proteins are secreted by the notochord to inhibit BMP-4 signaling?

Chordin, noggin, and follistatin. Signup and view all the answers

How does ectoderm differentiate into neuronal cells?

Automatically unless inhibited by BMP-4. Signup and view all the answers

Which of the following best describes the dermal skeleton?

It is compact, layered bone and may include enamel. Signup and view all the answers

In which type of embryos is primary neurulation technically applicable?

Only in tetrapods. Signup and view all the answers

The ceratohyal contributes to which adult structure?

Hyoid bone Signup and view all the answers

What features do the stapes and malleus share regarding their embryonic origins?

Both are derived from embryonic cartilage structures. Signup and view all the answers

What distinguishes primary neurulation from secondary neurulation?

Secondary neurulation occurs later in development. Signup and view all the answers

What is indicated by the anterior expression boundary within the neural tube?

It is associated with Hox gene expression patterns. Signup and view all the answers

Which of these skeletal elements is NOT present in adults but exists in embryos?

Meckel's cartilage Signup and view all the answers

Which arch of the viscerocranium is associated with the jaw joint in vertebrates?

Mandibular arch Signup and view all the answers

In which vertebrate group is there likely to be a lack of endochondral bones within the skull?

Mammals Signup and view all the answers

What represents the function of neural crest cells in the development of cranial structures?

They migrate from hindbrain regions to form various cranial arches. Signup and view all the answers

What does the outer blastoderm differentiate into during the early stages of mammalian development?

Trophoblast and inner cell mass Signup and view all the answers

What is a significant complication of placenta accreta?

Heavy haemorrhaging during delivery Signup and view all the answers

During gastrulation, which structure forms from the blastopore in deuterostomes?

Anus Signup and view all the answers

Which animal is NOT listed as having a representative example in the transition from blastula to gastrula?

Cat Signup and view all the answers

What extreme intervention may be required in cases of severe placenta accreta?

Hysterectomy Signup and view all the answers

What is a common pathology associated with neural crest cell population defects?

Reduction in the number of cells in NCC populations Signup and view all the answers

Which term refers to the stage characterized by the differentiation of tissues in mammals following fertilization?

Blastulation Signup and view all the answers

What type of cleft palate results from failure of neural crest cells to meet along the ventral midline?

Midline cleft palate Signup and view all the answers

Which of the following structures primarily forms from the trophoblast?

Placenta Signup and view all the answers

Which of the following is NOT a characteristic feature of Down Syndrome?

Protruding jaw Signup and view all the answers

What chromosomal abnormality is associated with Down Syndrome?

Partial or full duplication of the 21st pair of chromosomes Signup and view all the answers

What common characteristic is observed in the blastula to gastrula transition across various animal species?

It shows uniformity despite differences between species Signup and view all the answers

In cases of cleft palates, what is the potential implication of unilateral cleft palate?

Failure of bilateral neural crest cell streams to meet Signup and view all the answers

What is a common congenital issue associated with Down Syndrome?

Congenital heart problems Signup and view all the answers

Which type of cleft palate is characterized by bilateral failure of neural crest cell streams?

Paramedian cleft palate Signup and view all the answers

What is a typical feature of the facial structure in individuals with Down Syndrome?

Elongate orbits Signup and view all the answers

What is the term used to describe the phase-shift in sacral morphologies?

Onset of sacral morphologies Signup and view all the answers

In the context of vertebral column re-segmentation, what induces separation along the middle of the initial somites?

Ventral roots of spinal nerves Signup and view all the answers

Which condition involves the reactivation of the Varicella zoster virus after being dormant?

Shingles Signup and view all the answers

What was the specific injury Peyton Manning suffered during the 2011 NFL season?

Cervical disc herniation Signup and view all the answers

What type of radiculopathy did Manning experience resulting in numbness and weakness?

C7 radiculopathy Signup and view all the answers

How is the pathogen from shingles characterized when it reactivates?

It travels along nerve pathways. Signup and view all the answers

The mapping of spinal sensory and motor nerve roots is based on what anatomical structures?

Dermatome maps Signup and view all the answers

What is the primary outcome of the re-segmentation process in the vertebral column?

Formation of adult vertebral bodies Signup and view all the answers

Study Notes

Deuterostome Developmental Biology

Deuterostomes are a type of animal, mostly encompassing vertebrates.
The development of vertebrates shares similarities with other types of animals.

Reference Frame

Reference frames are equally valid in the absence of specific information.
Coordinate systems should be treated as artificial constructs.

Biological Reality

Directional reference (top, bottom, left, right, and front) in a fertilized ovum is defined by anatomical positioning.
These directions are fixed by birth, so top, bottom, left, right, and front are definable in a human.

Vertebrate Body Plan

Vertebrate development involves definitive top/bottom, left/right, front/back axes.
The body plan of a vertebrate develops from a single-celled ovum.

Vertebrate Phylogeny

Bilaterally symmetrical animals
Protostomes (blue)
Deuterostomes (red)

Echinoderms

Literally "spiny skin"
Possess a calcium carbonate endoskeleton in the dermis.
Diverse, both taxonomically and morphologically.

Hemichordates

Literally "half-chordates."
Include acorn worms and pterobranchs.
Not very diverse taxonomically but an interesting group.

Tunicates

Include sea squirts and salps.
Urochordates, members of the Chordata but not vertebrates.

Vertebrates: Petromyzontiformes (Lampreys)

True vertebrates with no bones.

Vertebrates: General

These animals exhibit a vertebrate body plan with bones.

Deuterostome Body Plan

Living body plans exhibit a wide variety and disparity.
Sea squirts, sea stars, and giraffes share some unifying characteristics.

Embryogenesis

Shared characteristics of deuterostomes emerge in early embryogenesis.

The Five Characters Uniting Chordata

Notochord
Dorsal hollow nerve cord
Pharyngeal slits in the pharynx
Postanal tail
Endostyle/thyroid
Not all taxa have these five features in their adult form.

Ontogeny

Ontogeny is the developmental history of an individual.
Development in the process of going through all stages of form from fertilization to adulthood is a unifying concept in comparative biology.
Evolution results from changes to development, which are ultimately at the level of genes.
Most of development is conserved.

Cleavage

Synchronous cell division.
Radial cleavage.

Blastulation

The morula hollows out.
Germ layer specification.
Basic axis polarity formation.

Gastrulation

Cells change shape and move inward to form archenteron,
Other cells break free and become mesenchyme.
Thin extensions of mesenchyme cells attach to the overlying ectoderm.
The archenteron elongates, assisted by mesenchyme cells
The mouth forms where the archenteron meets the ectoderm.
The blastopore becomes the anus during development.

Differentiation of the Mesoderm

Ectoderm and endoderm arise during gastrulation.
Mesoderm differentiation varies between protostomes and deuterostomes.

Gastrulation (in a frog)

Morphological developments are observed in Xenopus.
Cells undergo convergent extensions, involution, and epiboly.

Examples of Animal Embryology (blastula to gastrula)

Frog, snail, and fruit fly embryos.
Transitions are fairly uniform during animal development.

Neurulation

Notochord induces formation of neurectoderm (neural plate), creating a hollow neural tube.
Ectoderm differentiates to become the nervous system.
BMP-4 signaling plays a role in ectoderm differentiation between skin and neural cells.

Primary vs. Secondary Neurulation

Primary neurulation: Hollow neural tube is formed through invagination of neural plate.
Secondary neurulation: Solid neural cord is formed by ventral thickening of neural plate, which is subsequently hollowed out.

Retained Medullary Cord

Normal human development is characterized by primary and secondary neurulation of a medullary cord.
A spinal cord will be found in humans at the L₁/L₂ level.
The adult human spinal cord continues to the tailbone.

Neurulation (Brain Development)

Three primary embryonic brain regions: Prosencephalon (forebrain), Mesencephalon (midbrain), Rhombencephalon (hindbrain).

Neural Tube Defects (NTDs)

NTDs, such as spina bifida, result from neural tube closure failures.
Hydrancephaly: Failure of brain structure formation.
Anencephaly: Absence of brain formation.

The Neural Crest

Neural crest cells (NCCs) are derived from the neurectoderm.
NCCs migrate.
Patterns of NCC migration are conserved.
NCCs contribute to many vertebrate structures.

The Cranium

Embryonic components
Neurocranium supports paired sensory capsules.
Braincase/cranial elements
Cartilages form around sensory capsules (otic, optic, and olfactory).

The Arches

Mandibular arch: forms jaws
Hyoid arch: forms parts of the throat and larynx
Gill arches: forms gill structures.

Dermal Bones of the Face and Head

Structures form from streams of neural crest cells from the hindbrain.
Includes maxillary and mandibular bones.
Dermal bone development varies between mammals.

Intramembranous Ossification

Dermal bones form in humans via intramembranous ossification.
In the mandible, Meckel's cartilage is resorbed.

3D Models of the Middle and Inner Ear

3D models of the ear show conservation of the jaw joint between the articular and quadrate bones

The Vertebral Column

Re-segmentation of vertebral column leads to somite formation.
Sensory and motor nerve roots originate between the vertebra.
Spinal nerve roots have different patterns in various body regions.

Hox Genes and Vertebral Patterning

Number of each vertebrae type varies across species.
Vertebral patterns reflect Hox gene expression patterns.
Similar patterns among different vertebrate species, but some variances do exist.

Down Syndrome

Partial or full duplication of chromosome 21 features widened set eyes, elongated orbits and a smaller or absent nasal bridge.
Heart defects, hearing impairments, and palate clefts are also common.

DiGeorge Syndrome

Deletion of chromosome 22 causes congenital heart problems, such as persistent truncus arteriosus, ventricular septal defect, and right ventricular hypertrophy.
Symptoms include cleft palate and thyroid hypoplasia.

Patau Syndrome

Duplication or full duplication of chromosome 13 is associated with severe conditions, including heart defects and facial clefts (cleft palate, etc).
Most individuals do not survive past the first year of life

Waardenburg Syndrome

Mutated neural crest cells causes an increased interorbit distance, uneven orbits, and prominent white forelock.
Hearing loss is a frequent symptom.

Hirschsprung's Disease

Failure of neural crest cells to migrate to the entire intestine leads to a section of intestine that cannot relax.
This results in a digestive impairment that might need surgical intervention to correct.

Cleft Palate

Failure of left and right neural crest cells in the frontonasal prominence to meet along the ventral midline.
Can result in different severities of cleft palate.

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Description

This quiz explores key aspects of chordate development, including the functions of pharyngeal slits, postanal tail formation, and the role of the endostyle in filter feeding. Test your knowledge on the canonical characters shared by all chordates and the significance of Hox genes during embryonic development.