Chapter 34 Bio 191

diffusion

The random thermal motion of particles in liquids, gases, or solids; in the presence of a concentration or electrochemical gradient, results in the net movement of a substance from an area of higher concentration to an area of lower concentration

gastrovascular cavity

A central cavity with a single opening in certain animals, including cnidarians and flatworms, that functions in both digestion and nutrient distribution

heart

A muscular pump that uses metabolic energy to increase the hydrostatic pressure of blood or hemolymph, allowing circulatory fluid to flow throughout the body and eventually return to the heart

open circulatory system

A circulatory system in which hemolymph directly bathes tissues and organs, with no distinction between circulating fluid and interstitial fluid

hemolymph

The body fluid in invertebrates with an open circulatory system that directly bathes tissues

closed circulatory system

A circulatory system in which blood is confined to vessels and remains separate from the interstitial fluid

blood

A connective tissue with a fluid matrix called plasma, containing red blood cells, white blood cells, and cell fragments called platelets

cardiovascular system

A closed circulatory system consisting of a heart and a branching network of arteries, capillaries, and veins; characteristic of vertebrates

artery

A blood vessel that carries blood away from the heart to organs throughout the body

capillaries

Microscopic blood vessels that penetrate tissues and consist of a single layer of endothelial cells, allowing exchange between blood and interstitial fluid

veins

(1) In animals, blood vessels that carry blood toward the heart. (2) In plants, vascular bundles found in leaves

single circulation

A circulatory system consisting of one pump and one circuit, in which blood passes from gas exchange organs to the rest of the body before returning to the heart

double circulation

A circulatory system consisting of separate pulmonary and systemic circuits, in which blood passes through the heart after completing each circuit

cardiac cycle

The alternating contractions and relaxations of the heart

vasoconstriction

A decrease in the diameter of blood vessels caused by contraction of smooth muscles in vessel walls

vasodilation

An increase in the diameter of blood vessels caused by relaxation of smooth muscles in vessel walls

pulse

The rhythmic expansion and bulging of artery walls with each heartbeat

lymphatic system

A system of vessels and nodes, separate from the circulatory system, that returns fluid, proteins, and cells to the blood

lymph

The colorless fluid derived from interstitial fluid that circulates through the lymphatic system of vertebrates

lymph node

An organ located along a lymph vessel that filters lymph and contains immune cells that attack viruses and bacteria

gas exchange

The uptake of molecular oxygen from the environment and the release of carbon dioxide into the environment

ventilation

The movement of air or water over a respiratory surface

countercurrent exchange

The exchange of a substance or heat between two fluids flowing in opposite directions; maximizes diffusion efficiency, such as oxygen uptake in fish gills

tracheal system

In insects, a system of branched, air

lung

An infolded respiratory surface of a terrestrial vertebrate, land snail, or spider that connects to the atmosphere through narrow tubes

larynx

The portion of the respiratory tract containing the vocal cords; also called the voice box

trachea

The portion of the respiratory tract that extends from the larynx to the bronchi; also called the windpipe

bronchus

One of a pair of breathing tubes that branch from the trachea into the lungs; plural: bronchi

alveolus

One of the small, dead

surfactant

A substance secreted by alveoli that decreases surface tension in the fluid coating the alveoli, preventing them from collapsing

breathing

The ventilation of the lungs through alternating inhalation and exhalation

diaphragm

A sheet of muscle forming the bottom wall of the thoracic cavity in mammals; contraction pulls air into the lung

Compare and contrast open and closed circulatory system and which groups of animals have each

1. Open Circulatory System

• Circulatory fluid (called hemolymph) is NOT always contained within blood vessels.

• The heart pumps hemolymph into open body spaces called sinuses, where it directly bathes organs and tissues.

• Generally operates at lower pressure and is less efficient at transporting materials quickly.

• Requires less energy to maintain.

Animal groups that have open circulatory systems:

• Arthropods (insects, spiders, crustaceans)

• Most mollusks (snails, clams)

2. Closed Circulatory System

• Blood is ALWAYS contained within blood vessels.

• The heart pumps blood through a network of arteries, veins, and capillaries.

• Allows higher blood pressure and faster, more efficient delivery of oxygen and nutrients.

• Supports animals with higher metabolic demands.

Animal groups that have closed circulatory systems:

• Annelids (earthworms)

• Cephalopods (octopuses and squids)

• Vertebrates (fish, amphibians, reptiles, birds, mammals)

Define the 3 main types of blood vessels- describe where they are primarily located and the direction that blood moves through them

1. Arteries

• Function: Carry blood AWAY from the heart.

• Structure: Thick, muscular, elastic walls to withstand high blood pressure.

• Location: Carry blood from the heart toward body organs and tissues.

• Direction: Heart → Body.

• Usually carry oxygen-rich blood (exception: pulmonary arteries).

2. Veins

• Function: Carry blood TOWARD the heart.

• Structure: Thinner walls, larger internal spaces (lumens), and valves that prevent backflow.

• Location: Return blood from body tissues and organs back to the heart.

• Direction: Body → Heart.

• Usually carry oxygen-poor blood (exception: pulmonary veins).

3. Capillaries

• Function: Allow exchange of oxygen, carbon dioxide, nutrients, and wastes between blood and body tissues.

• Structure: Extremely thin walls, only one cell thick, allowing substances to diffuse across.

• Location: Form networks throughout body tissues, connecting arterioles to venules.

• Direction: Arterioles → Capillaries → Venules.

Compare and contrast single and double circulation and which groups of animals have each

• Single = 1 trip through the heart → Fish.

• Double = 2 trips through the heart → Amphibians, reptiles, birds, mammals.

Define and describe the cardiac cycle

1. Atrial Systole (Atria Contract)

• The atria contract, pushing blood into the ventricles.

• The atrioventricular (AV) valves are OPEN.

• The semilunar valves are CLOSED.

• Ventricles finish filling with blood.

2. Ventricular Systole (Ventricles Contract)

• The ventricles contract, increasing pressure inside the heart.

• The AV valves CLOSE to prevent blood from flowing backward into the atria.

• The semilunar valves OPEN.

• Blood is pumped out:

  • Right ventricle → Pulmonary artery → Lungs.

  • Left ventricle → Aorta → Rest of body.

3. Complete Diastole (Heart Relaxes)

• Both the atria and ventricles relax.

• The semilunar valves CLOSE to prevent blood from flowing backward into the ventricles.

• The AV valves OPEN.

• Blood flows from the veins into the atria and then into the ventricles.

Understand the functions of 3 main types of blood vessels (arteries, capillaries, veins) (34.3)

▪ Diameter

▪ Area

▪ Blood velocity

▪ Blood pressure

Characteristic	Arteries	Capillaries	Veins
Diameter (individual vessel)	Medium	Smallest	Largest
Total cross-sectional area	Low	Highest	Low
Blood velocity	Fast	Slowest	Faster than capillaries
Blood pressure	Highest	Low	Lowest
Main function	Deliver blood	Exchange materials	Return blood

Describe the function of gills and countercurrent exchange

• Gills = Extract oxygen from water and release carbon dioxide.

• Countercurrent exchange = Water and blood flow in OPPOSITE directions to maximize oxygen absorption.

Describe the function of the tracheal system

• Spiracles: Small openings on the body surface that allow air to enter and exit.

• Tracheae: Larger branching tubes that carry air throughout the body.

• Tracheoles: Tiny branches that extend close to individual cells, allowing oxygen and carbon dioxide to diffuse directly between the air and tissues.

Briefly describe the process of breathing in different animal groups

Animal group	Breathing mechanism
Fish	Gills; countercurrent exchange
Insects	Spiracles → tracheae → tracheoles
Mammals	Diaphragm and rib muscles; negative-pressure breathing
Birds	Lungs and air sacs; one-way airflow
Amphibians	Positive-pressure breathing and skin
Reptiles	Rib movements expand and contract lungs