Circulatory & Digestive Systems – Practice Flashcards

A curated set of question-and-answer flashcards covering bulk flow, circulatory system types, vessel anatomy, blood composition, hemoglobin dynamics, vertebrate hearts, metabolic scaling, feeding strategies, essential nutrients, and digestive tract adaptations discussed in the lecture.

What is bulk flow in the context of gas transport?

The coordinated movement of large volumes of fluid or gas (e.g., inhaled air, blood) driven by pressure differences, distinct from molecular diffusion.

Name the three fundamental components of any circulatory system.

1) Muscular pump (heart), 2) Circulatory fluid (blood or hemolymph), 3) Vessels or conduits.

List four major substances transported by blood besides oxygen and carbon dioxide.

Nutrients, metabolic waste, hormones, and immune cells (white blood cells / leukocytes).

How does an open circulatory system differ from a closed one?

Open systems dump fluid into body cavities (hemocoels) where it bathes organs; closed systems keep blood entirely within continuous vessels.

Give one invertebrate group that typically has an open circulatory system and one that has a closed system.

Open – most arthropods (e.g., insects, crustaceans); Closed – annelids (e.g., earthworms).

What is hemolymph?

The circulatory fluid in many open systems; functions like blood but spills into body cavities.

What are ostia in an arthropod heart?

Valve-like openings that allow hemolymph to re-enter the heart during refilling.

Why don’t most terrestrial insects need a circulatory system for oxygen delivery?

They use a tracheal tube network that brings atmospheric air directly to individual cells.

Which molluscan class possesses a closed circulatory system?

Cephalopods (e.g., squid and octopus).

Why can sponges, cnidarians, and sea stars survive without a true circulatory system?

They live in water, have thin tissues or internal canals, and rely on direct diffusion (plus a water vascular system in echinoderms).

What are the three hearts of a squid called and what is their function?

Two branchial (gill) hearts pump blood through the gills; one systemic heart propels oxygenated blood to the body.

Primary distinction between an artery and a vein?

Direction of flow: arteries carry blood away from the heart; veins carry blood toward the heart (oxygen content can vary).

Define ‘lumen’ and ‘endothelium’ in blood vessels.

Lumen – the hollow interior where blood flows; Endothelium – single epithelial cell layer lining the lumen.

Why are large arteries rich in elastic connective tissue?

To stretch and recoil under high pressures generated by ventricular contraction.

Function of venous valves in medium–large veins?

Prevent back-flow of low-pressure blood, especially against gravity.

Why are capillary walls extremely thin?

A single endothelial layer minimizes diffusion distance, maximizing exchange of gases, nutrients, and wastes (Fick’s law).

What regulates blood distribution through a capillary bed?

Pre-capillary sphincters (rings of smooth muscle) controlled by the autonomic nervous system.

Main cellular and non-cellular components of blood.

Cellular – erythrocytes (RBCs), leukocytes (WBCs); Non-cellular – platelets, plasma (water, proteins, nutrients, gases, waste).

What metal ion gives hemoglobin its red color when oxygenated?

Iron (Fe).

Which respiratory pigment contains copper and turns blue when oxygenated?

Hemocyanin, found in many crustaceans and some mollusks (e.g., horseshoe crabs).

Why is carbon monoxide (CO) poisoning dangerous at the molecular level?

CO binds to hemoglobin’s O₂ site with higher affinity than oxygen, preventing oxygen transport.

How does rising tissue CO₂ promote oxygen unloading from hemoglobin?

CO₂ binds to hemoglobin (different site), lowers O₂ affinity, and shifts partial-pressure gradients toward tissue uptake.

Typical chamber counts for fish, amphibians, and mammals/birds?

Fish – 2 chambers; Amphibians – 3 chambers; Mammals/Birds – 4 chambers (2 atria, 2 ventricles).

Differentiate pulmonary and systemic circuits in vertebrate circulation.

Pulmonary moves blood between heart and lungs/gills; systemic moves blood between heart and body tissues.

What does the ‘mouse-to-elephant curve’ illustrate?

Mass-specific metabolic rate decreases as body size increases; tiny animals need more energy per gram than large ones.

Implication of the mouse-to-elephant curve for drug dosing?

Medicinal doses cannot be scaled linearly by weight; small animals metabolize drugs faster per mass unit than large animals.

Define suspension feeding and give a marine example.

Filtering small particles from water; example – gray whale using baleen to sieve tons of krill.

Essential nutrient definition and example important for vision.

A molecule an animal cannot synthesize and must ingest; e.g., Vitamin A derived from carotenoids.

Which macronutrient stores the most energy per gram and why?

Triglycerides (lipids) because they contain many C-H bonds with high potential energy.

Why is heat an unavoidable by-product of metabolism?

Breaking chemical bonds to make ATP is inefficient; excess energy is released as thermal energy (heat loss).

How is metabolic rate commonly measured in lab settings?

By measuring oxygen consumption rate, which correlates with heat production.

Explain the U-shaped oxygen-consumption curve in flying birds.

High energy to initiate flight, lower cost at cruising speed, then increasing cost again as speed rises due to wind resistance.

What are brush-border cells and their role in digestion?

Enterocytes lining the small-intestine villi whose microvilli bear digestive enzymes and absorb nutrients into blood/lymph.

Which digestive region performs most enzymatic breakdown of food?

The duodenum (early segment of the small intestine).

How are dietary fats transported away from the intestine?

As chylomicrons entering lymphatic vessels (lacteals) because they are too large for blood capillaries.

Why do herbivores generally have longer intestines and larger ceca than carnivores?

To provide more surface area and house symbiotic microbes needed for cellulose fermentation.

What is a rumen, and what is its ecological purpose?

A fore-stomach chamber in ruminants (e.g., cows, bison) that hosts microbes to digest cellulose before true stomach digestion.

How do zebras digest cellulose without a rumen?

They are hind-gut fermenters; an enlarged colon/cecum houses microbes that ferment plant material.