Long Exam 2

Introduction to the Animal Body

  • Anatomy is the biological form of an organism.

  • Physiology is the biological functions an organism performs.

  • Homeostasis is used to maintain a “steady state” or internal balance regardless of the external environment. In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level.

    • Mechanisms of Homeostasis:

      • Control changes in the internal environment.

      • Fluctuations above or below a set point serve as a stimulus; these are detected by a sensor and trigger a response.

      • The response returns the variable to the set point.

    • Homeostasis in animals relies largely on negative feedback, which helps to return a variable to a normal range.

  • Positive feedback amplifies a response or process, moving a system away from its starting state. It tends to enhance or accelerate changes in the body and does not usually contribute to homeostasis. For example, during childbirth, the release of oxytocin increases contractions, which leads to more oxytocin release.

  • Negative feedback counteracts a change, helping to return a system to its set point or normal range. This is crucial for maintaining homeostasis. For instance, if body temperature rises, mechanisms such as sweating are activated to lower the temperature back to a set point.

Alterations in Homeostasis

  • Set points and normal ranges can change with age or show cyclic variation.

  • In animals and plants, a circadian rhythm governs physiological changes roughly every 24 hours.

  • Homeostatic processes for thermoregulation involve form, function, and behavior:

    • Thermoregulation: animals maintain an internal temperature within a tolerable range.

    • Endothermic: animals generate heat by metabolism; birds and mammals are endotherms.

    • Ectothermic: animals gain heat from external sources; ectotherms include most invertebrates, fishes, amphibians, and nonavian reptiles.

  • Acclimatization: the process by which homeostasis can adjust to changes in the external environment.

  • Poikilotherm: body temperature varies with its environment.

  • Homeotherm: body temperature is relatively constant.

  • Organisms exchange heat by four physical processes: Radiation, Evaporation, Convection, and Conduction:

    1. Radiation: The transfer of heat in the form of electromagnetic waves. For example, organisms can gain heat from the sun without direct contact.

    2. Evaporation: The process of losing heat when liquid water converts to vapor. This cooling effect is evident when animals sweat or when water evaporates from surfaces.

    3. Convection: The movement of heat through fluids (liquids and gases) as warmer, less dense areas rise and cooler, denser areas descend. For instance, a warm breeze can transfer heat away from an animal, aiding in cooling.

    4. Conduction: The direct transfer of heat between objects in contact. When an organism sits on a warm rock, heat is conducted from the rock to the organism's body, increasing its temperature.


Tissues

  • Different tissues have varying structures that are suited to their functions.

  • Tissues are classified into four main categories: Epithelial, Connective, Muscle, Nervous.

Epithelial Tissues:

  • covers the outside of the body and lines the organs and cavities within the body.

  • Shape: cuboidal, columnar, or squamous

  • Arrangement: may be simple (single layer), stratified (multiple layers), or pseudostratified (a single layer of cells of varying length).

Simple squamous epithelium - allows transport across membranes in lungs and capillaries, secretes fluid in serous membranes, covers organs

Simple cuboidal epithelium - consists of a single layer of cube-shaped cells. This type of epithelial tissue is often involved in secretion and absorption. Common locations include glands, kidney tubules, and the surface of the ovaries.

Simple columnar epithelium - Simple columnar epithelium consists of a single layer of tall, column-like cells. This type of epithelial tissue is involved in absorption and secretion. It is commonly found in the digestive tract (stomach lining)

Pseudostratified columnar epithelium - single layer of cells that appear to be stratified due to varying cell heights, giving the illusion of multiple layers. This type of epithelial tissue is often ciliated and is primarily found lining the respiratory tract

Stratified squamous - Can be found in the skin; keratinized meaning it has keratin


Connective Tissues

  • Mainly binds and supports other tissues

  • Contains sparsely packed cells scattered throughout an extracellular matrix

  • The matrix consists of fibers in a liquid, jellylike tr solid foundation

  • Three types of connective tissues

    • Collagenous fibers - provide strength and flexibility

    • Reticular fibers - join connective tissue to adjacent tissues

    • Elastic fibers - stretch and snap back to their length

  • Connective tissues contain cells including

    • Fibroblasts - secretes the protein of extracellular fibers

    • Macrophages - involved in the immune system

Types of connective tissue:

Loose (areolar) - connective tissues bind epithelia to underlying tissues and hold organs in place

Dense (Fibrous) - found in tendons that attach muscles to bones, and ligaments which connect bones to cones

Adipose Tissue - store fats for insulation and fuel (can be found in breasts)

Blood - composed of blood cells and cell fragments in blood plasma

Cartilage - connective tissue for strong and flexible support material

Bone - mineralized and forms the skeleton


Muscle Tissues

  • Responsible for nearly all types of body movement

  • Muscle cells consist of filaments of the proteins actin acid and myosin, which together enable muscles to contract.

  • Divided into three types: skeletal, cardiac, and smooth

Skeletal - also called striated muscles responsible for voluntary movements.

Cardiac - responsible for the contraction of the heart; has intercalated disks

Smooth - responsible for involuntary activities.


Nervous Tissue

  • Functions in the receipt, processing, and transmission of information

  • Nervous tissue contains:

    • neurons or nerve cells that transmit nerve pulses

    • Glial cells or glia which are support cells.


Integumentary System

  • The integument is the outer covering of the body.

  • Includes the skin and all structures derived from or associated with the skin such as hair, setae, scales, feathers, and horns

  • Many invertebrates have single layered epidermis covering the body. Other have added secreted non-cellular cuticle over the epidermis

  • Molluscs have a delicate epidermis and need shells for protection.

  • Exoskeletons are part of this system, not skeletal system.

Two distinct layers (epidermis and dermis)

Four types of cells:

  • Keratinocytes - deepest, produce keratin (tough fibrous protein)

  • Melanocytes - produce melanin and make skin dark

  • Merkel cells - associated with nerve endings

  • Squamous epithelium

Layers of the epidermis (from superficial to deep)

Stratum corneum - horny layer (dead cells, many layers thick)

Stratum granulosum - layers of flattened keratinocytes producing keratin (hair and nails)

Stratum spinosum - spinyness is artifactual; tonofilaments (bundles of protein) resist tension

Stratum germinativum/ basale - single row of cells attached to the dermis; youngest cells.

Note: Epidermis is made up of epithelial tissues while the dermis is made up of connective tissues.

Characteristics of the Dermis:

  • Strong flexible connective tissue

  • Cells: fibroblasts, macrophages, mas cells, WBCs

  • Fiber types: collagen, reticular, elastic

  • Rich supply of nerves and vessels

  • Role in temperature regulation

  • Two layers

    • Papillary (upper) - loose connective tissue; includes dermal papillae (ridges which gives fingerprints)

    • Reticular (lower) - “reticulum” (network) of collagen and reticular fibers

Note: Thick skin will contain stratum lucidum while thin skin won’t.

Skin Appendages

  • Derived from the epidermis but extend into the dermis. This includes:

    • hair and hair follicles

    • Sebaceous (oil) glands

    • Sweat glands

    • Nails

Nails

  • hard keratin

  • corresponds to hooves and claws in lower-order animals

  • grows from the nail matrix

Hair and Hair Follicle Complex

  • Grows everywhere except palms, soles, nipples, and parts of the genitalia

  • Functions: warmth, sense light tough of the skin, protection (scalp)

  • Parts

    • Root - embedded in skin

    • shaft - projecting above skin surface

  • Make up of hair - hard keratin

  • Three concentric layers

    • Medulla (core)

    • Cortex (surrounding the medulla)

    • Cuticle (single layers, overlapping)

Sweat Glands

  • entire skin surface expect nipples and part of the genitalia

  • prevent overheating

  • 500cc to 12L/day (mostly water)

  • Only mammals have sweat glands and humans are most efficient

  • Produced in response to stress as well as heat

Skin Color

  • Three skin pigments

    • Melanin: most important as it protect skin from the sun

    • Carotene: from carrots and yellow vegetables

    • Hemoglobin: the pink of light skin

  • Melanin in granules passes from melanocytes in the dermis (same number in all races) to keratinocytes in the stratum basale

  • Digested by lysosomes

  • Variations in color

  • protection from UV light



    Skeletal System


  • the Skeleton provides rigid structure to which muscles attach.

  • Skeletons function in support, protection, and movement.

  • Three types of skeletal system:

    • Hydrostatic skeleton (lacks hard parts)

    • Exoskeleton (external hard parts)

    • Endoskeleton (internal hard parts)

Hydrostatic skeleton

  • consists of fluid held under pressure in a closed body compartment

  • main type of skeleton in most cnidarians, flatworms, nematodes, and annelids

  • Annelids use their hydrostatic skeleton for peristalsis, a type of movement produced by rhythmic waves of muscle contractions from front to back

Exoskeleton

  • a hard encasement deposited on the surfaces of an animal

  • found in most molluscs and arthropods

  • Arthropods

    • jointed exoskeleton called a cuticle, which can be both strong and flexible

    • The polysaccharide chitin is often found in arthropod cuticle

Endoskeleton

  • consist of a hard internal skeleton, buried in soft tissue

  • found in organisms ranging from sponges to mammals

  • A mammalian skeleton has more than 200 bones

  • Some bones are connected at joints by ligaments that allow freedom of movement


  • A ball and socket joint is a type of joint that allows for radial movement in almost any direction; it consists of a spherical end (ball) that fits into a cupped cavity (socket) in another bone. Examples include the shoulder and hip joints.

  • A hinge joint permits motion in one plane, allowing for bending and straightening; it resembles a door hinge. The elbow and knee joints are prime examples of hinge joints.

  • A pivot joint allows for rotational movement around a single axis; it enables one bone to rotate around another. An example of a pivot joint is found in the neck (between the first and second vertebrae), allowing for the ability to turn the head from side to side

Bone is a living tissue that differs from other connective and supportive tissues by having significant deposits of inorganic calcium salts laid down in an extracellular matric composed of collagenous fibers in a protein-sugar gel.

The vertebrate skeleton is composed of two main divisions:

Axial - Skull, Vertebral Column, sternum, and ribs

Appendicular - pectoral girdle, pelvic girdle, and appendages


Long Bones

Epiphysis of a long bone is at either end of it.

  • Consists chiefly of spongy bone with a thin outer layer of compact bone

  • Epiphyseal plate/line (physis) is composed of hyaline cartilage and represents the point of growth in a longitudinal direction

    • dictates your growth

Diaphysis is the cylindrical shaft of a long bone between either epiphysis.

  • Contains marrow (medullary) cavity surrounded by a thick wall of compact bone

  • Site of red blood cell production

Endosteum is the lining tissue of all surfaces of the bone that face the medullary cavity and also the trabeculae of the bone.

  • Only 1 cell layer thick and the cells can become osteoblasts (forms the osteocyte or mature bone cell) when stimulated

Periosteum

  • Increase in diameter of bones, aids in healing fracture

  • has osteoblasts - forms bone cells


    Haversian System

  • The unit of structure of compact bone

  • Composed of central haversian canal surrounded by concentric laters of bone called lamellae

  • Osteocytes are contained within small cavities known as lacunae

  • Osteocytes communicate with each other and with the haversian canal through a branching network of canals knows as the canaliculi

Osteoprogenitor cells - comprise the population of cells n the innermost layer of the periosteum, the endosteal lining of cells of the marrow cavities, and the lining cells of the Haversian canals and Volkman’s canals.

Osteoblast - differentiated bone-forming cells responsible for the production of the bone matrix. Its secretion of collagen and ground substance makes up the initial unmineralized bone or osteoid. Also associated with calcification of the matrix.

Osteocytes - mature bone cells, represents transformed osteoblasts, it is enclosed by the bone matrix that it had previously laid down. Maintains bone matrix

Growth of Long Bones

  • Increase in bone length depends on the presence of the epiphyseal plate wherein four zones are recognized which extend from the epiphysis to the diaphysis.

    1. Proliferation Zone: Chondroblasts quickly divide and push the epiphysis away from the diaphysis, lengthening the bone.

    1. Hypertrophic zone: older chondrocytes enlarge and signal the surrounding matrix to calcify

    2. Calcification zone: matrix becomes calcified and chondrocytes die that leave behind trabeculae-shaped calcified cartilage. Not yet bone.

    3. Ossification zone: osteoclasts digest the calcified cartilage and osteoblasts replace it with actual bone tissue in the shape of the calcified cartilage resulting in bone treabulae.

Bone Repair

  • bone fractures result in disruption of the blood supply and the osteocytes begin to die leading to necrosis of the periosteum and marrow.

  • This is followed by an acute inflammatory reaction that brings phagocytic cells into clear blood clots and necrotic tissue

Muscular System

Smooth Muscle

  • Lacks striation

  • Cells are much smaller, tapering strands, with a single, centrally-located nucleus

  • Responsible for peristalsis, propelling, and regulating movement of substances

  • Contractions are involuntary and unconscious

Cardiac Muscle

  • Striated involuntary muscle

  • Found in the heart

  • Presence of intercalated discsVertebrate Skeletal Muscle Structure

Skeletal Muscle

  • Skeletal muscle is organized into a hierarchy of smaller units.

  • Each muscle is a bundle of long fibers, with each fiber being a single cell containing multiple nuclei (formed from fused embryonic cells).

  • Surrounding the nuclei are longitudinal myofibrils made up of bundles of thin and thick filaments.

  • Myofibrils consist of repeating sections called sarcomeres, the basic contractile units of skeletal muscle, which form a pattern of striations (light and dark bands).

Structure of a Skeletal Muscle

  • Epimysium - outermost tissue

  • Fasicle - bundle of muscle fibers

  • Perimysium - surrounds each fascicle

  • Endomysium - covers every muscle fiber in the fascicle

    • Every muscle fiber (or muscle cell) contains numerous myofibrils, which are long, thread-like structures that run the length of the cell. Myofibrils are composed of repeating units called sarcomeres, which are the fundamental contractile units of skeletal muscle.

Sarcomere Arrangement

  • Thin filaments attach at the Z lines at the ends of sarcomeres.

  • Thick filaments are anchored at the M line in the center of the sarcomere.

  • In a relaxed myofibril, thick (myosin) and thin (actin) filaments partially overlap.

  • At the edges, only thin filaments are present, while the center contains only thick filaments.

Sliding-Filament Model of Muscle Contraction

  • A contracting muscle shortens, but the filaments (thick and thin) do not change length; they slide past each other according to the sliding-filament model.

  • Myosin molecules power the sliding process, utilizing ATP.

  • Myosin heads bind to actin, forming cross-bridges, and pull thin filaments toward the center of the sarcomere.

  • Each myosin head attaches to a binding site on the thin filament, pulls, and releases with ATP; this cycle occurs repeatedly to sustain contraction.

Energy Sources for Muscle Contraction

  • Muscle fibers contain limited ATP for a few contractions; longer activity relies on creatine phosphate and glycogen.

  • The breakdown of creatine phosphate to ADP synthesizes ATP, providing energy for about 15 seconds.

  • Glycogen can be metabolized into glucose to generate ATP through aerobic respiration for nearly an hour during moderate activity.

  • In intense activity, lactic acid fermentation generates ATP anaerobically for about 1 minute.

Role of Calcium and Regulatory Proteins

  • In a resting muscle fiber, two key regulatory proteins—tropomyosin and the troponin complex—are bound to actin (part of the thin filaments in muscle).

  • Tropomyosin blocks the binding sites on actin where myosin (part of the thick filament) would attach. This prevents actin and myosin from interacting, so the muscle stays relaxed.

  • Role of Calcium (Ca²⁺):

    • When a motor neuron signals a muscle fiber to contract, it releases calcium ions (Ca²⁺) into the cytosol (the fluid inside the muscle cell).

    • Ca²⁺ binds to the troponin complex, which causes a shape change that moves tropomyosin away from the myosin-binding sites on actin.

  • Contraction Begins:

    • With the binding sites on actin now exposed, myosin can bind to actin, forming cross-bridges.

    • The cross-bridge cycle begins, allowing the thin and thick filaments to slide past each other, leading to muscle contraction.

  • Contraction Stops When Ca²⁺ Levels Drop:

    • When Ca²⁺ concentration in the cytosol decreases, Ca²⁺ unbinds from the troponin complex.

    • Tropomyosin moves back to cover the binding sites on actin, preventing further interaction with myosin, and the muscle relaxes.Skeletal Muscle Contraction Process

  1. Action potential arrives at motor neuron terminal, releasing acetylcholine.

  2. Acetylcholine binds to muscle fibers, leading to depolarization and an action potential.

  3. Action potential travels along T tubules, triggering the sarcoplasmic reticulum (SR) to release calcium ions.

  4. Calcium binds to troponin, starting muscle contraction.

    1. Muscle relaxes when calcium is pumped back into the SR, re-blocking the myosin-binding sites.


      Graded Contraction in Whole Muscles:

      • Unlike a single muscle fiber, which produces an all-or-none twitch, a whole muscle (e.g., biceps) can have varied, graded contractions.

      • The nervous system achieves this by:

        1. Varying the number of muscle fibers contracting.

        2. Modulating the rate of stimulation of muscle fibers.

      Motor Units and Recruitment:

      • Motor Unit: A motor neuron and all the muscle fibers it controls.

      • Each muscle fiber is controlled by one motor neuron; however, each motor neuron can connect to multiple muscle fibers.

      • When a motor neuron fires an action potential, all fibers in its motor unit contract together.

      • Recruitment of more motor units increases muscle tension, allowing for varied force, like lifting a light fork or a heavy textbook.

      Summation and Tetanus:

      • Summation: When action potentials occur before full relaxation of a muscle fiber, resulting in increased tension.

        • Twitch

        • Summation of two twitches

      • Tetanus: At high stimulation rates, muscle fibers cannot relax between stimuli, resulting in a smooth, sustained contraction.

      • Note: Tetanus is also a disease caused by a bacterial toxin leading to uncontrolled muscle contractions.

  • Oxidative vs. Glycolytic Fibers:

    • Oxidative Fibers:

      • Rely on aerobic respiration for ATP.

      • Contain many mitochondria, a rich blood supply, and high levels of myoglobin (an oxygen-binding protein), giving a reddish color.

      • These fibers resist fatigue and are found in "dark meat" in animals like poultry and fish.

    • Glycolytic Fibers:

      • Use glycolysis as their main ATP source.

      • Have larger diameters and less myoglobin.

      • Fatigue more easily and appear as "light meat" in animals.

  • Fast-Twitch vs. Slow-Twitch Fibers:

    • Fast-Twitch Fibers:

      • Contract quickly, developing tension 2-3 times faster than slow-twitch fibers.

      • Suited for brief, powerful contractions.

      • Can be either oxidative or glycolytic.

    • Slow-Twitch Fibers:

      • Contract more slowly and sustain longer contractions.

      • Have less sarcoplasmic reticulum (store and release calcium ions), causing Ca²⁺ to stay in the cell longer, leading to longer twitches.

      • Always oxidative and more fatigue-resistant.

  • Human Skeletal Muscle Composition:

    • Most human muscles have a mix of fast and slow fibers.

    • Muscles like those in the eye and hand are exclusively fast-twitch.

    • Genetics determines the proportion of fast and slow fibers, but training (especially endurance activities) can shift some fast glycolytic fibers into more fatigue-resistant fast oxidative fibers

Cardiovascular system

  • Basic Components of Circulatory Systems:

    • Circulatory fluid: Transports materials.

    • Interconnecting vessels: Channels through which fluid flows.

    • Muscular pump (heart): Powers circulation by using energy to create pressure, causing fluid to flow through vessels and return to the heart.

  • Functions of the Circulatory System:

    • Connects body cells to organs for gas exchange, nutrient absorption, and waste disposal.

    • In mammals, oxygen from the lungs reaches blood after passing through a few cell layers, then circulates to body tissues where it diffuses into cells.

  • Types of Circulatory Systems:

    • Open Circulatory System:

      • Circulatory fluid, called hemolymph, is not confined to vessels. Instead, the heart pumps hemolymph through vessels that open into sinuses, where it directly bathes the organs.

      • Found in arthropods (e.g., grasshoppers) and some molluscs.

      • Heart contraction pumps hemolymph into sinuses; heart relaxation draws it back through pores with valves to prevent backflow.

    • Closed Circulatory System:

      • Found in vertebrates; blood is confined to vessels, separate from interstitial fluid.

      • Hearts pump blood through branching vessels, enabling efficient exchange between blood, interstitial fluid, and cells.

  • Organization of Vertebrate Circulatory Systems:

    • Called the cardiovascular system in vertebrates, it includes the heart and extensive networks of blood vessels.

    • Types of Blood Vessels:

      • Arteries: Carry blood away from the heart; branch into arterioles leading to capillaries.

      • Capillaries: Thin-walled vessels that facilitate diffusion of gases and nutrients.

      • Veins: Return blood to the heart from capillaries.

    • Note: Arteries and veins are defined by direction of blood flow, not oxygen content.

  • Heart Structure:

    • All vertebrate hearts have two or more chambers: atria (receive blood) and ventricles (pump blood out).

    • Chamber structure and separation vary by species, reflecting adaptations from natural selection.

  • Pulmonary Circuit:

    • Right Ventricle pumps oxygen-poor blood to the lungs via pulmonary arteries.

    • Blood flows through capillary beds in the lungs, where it picks up O₂ and releases CO₂.

    • Oxygen-rich blood returns to the left atrium via the pulmonary veins.

  • Systemic Circuit:

    • From the left atrium, blood flows into the left ventricle, which pumps it through the aorta to the rest of the body.

    • Blood flows through capillary beds in organs, delivering O₂ to tissues and picking up CO₂.

    • Oxygen-poor blood returns to the heart via the superior and inferior vena cava into the right atrium.

  • Heart Structure:

    • Located behind the sternum, the heart has four chambers: two atria and two ventricles.

    • Atria collect returning blood, and ventricles pump it out forcefully, especially the left ventricle, which supplies the entire body.

    • Cardiac Cycle: The contraction phase is systole, and the relaxation phase is diastole.

  • Cardiac Output:

    • Determined by heart rate (beats per minute) and stroke volume (blood pumped per contraction).

    • Average cardiac output is around 5 L/min at rest, increasing significantly during exercise.

  • Heart Valves:

    • Atrioventricular (AV) valves lie between each atrium and ventricle, preventing backflow during ventricular contraction.

    • Semilunar valves at the heart's exits prevent backflow when the ventricles relax.

    • Valve closure creates the “lub-dup” sound of the heartbeat.

  • Heart Murmurs:

    • Caused by backflow through defective valves; can result from congenital issues or infections like rheumatic fever.

    • Severe valve defects may require surgical replacement.

  • Autorhythmic Cells:

    • Some cardiac muscle cells are autorhythmic, meaning they can generate their own contraction rhythm without external input.

    • These cells are crucial for the heart's ability to beat without direct nervous system control.

  • Sinoatrial (SA) Node (Pacemaker):

    • Located in the right atrium, near the entrance of the superior vena cava, the SA node acts as the heart's natural pacemaker.

    • It generates electrical impulses that set the rate and timing of heart contractions.

  • Electrical Impulse Propagation:

    • The electrical impulses generated by the SA node spread rapidly through the walls of the atria, causing both atria to contract in unison.

    • Cardiac muscle cells are electrically coupled through gap junctions, allowing impulses to spread efficiently.

  • Atrioventricular (AV) Node:

    • The impulse reaches the AV node, located between the atria, where it is delayed for about 0.1 second.

    • This delay ensures that the atria have enough time to empty completely into the ventricles before ventricular contraction.

  • Ventricular Conduction:

    • After the AV node, the electrical signals are transmitted to the heart apex and spread throughout the ventricular walls by specialized fibers called bundle branches and Purkinje fibers.

    • These fibers help coordinate the contraction of the ventricles.

  • Electrocardiogram (ECG or EKG):

    • The electrical activity of the heart can be measured using an electrocardiogram (ECG or EKG).

    • Electrodes placed on the skin detect the electrical currents generated by heart contractions, producing a graph that represents the stages of the cardiac cycle.

1.Capillaries:

  • Structure: Capillaries are the smallest blood vessels, with a diameter just large enough to accommodate a red blood cell. Their walls consist of a single layer of endothelial cells (endothelium) and a surrounding basal lamina (extracellular matrix), making them extremely thin.

  • Function: The thin walls allow for efficient exchange of gases, nutrients, and waste products between the blood and surrounding tissues. This exchange occurs because the capillary walls are permeable enough for molecules to diffuse through, providing a direct route for nutrients to reach cells and waste products to be carried away.

2. Arteries and Veins:

  • Structure: Both arteries and veins have thicker walls compared to capillaries. These walls consist of two layers around the endothelium:

    • The outer layer is made of connective tissue, providing strength and flexibility to the vessels.

    • The middle layer consists of smooth muscle cells and elastic tissue, allowing the vessels to contract and expand based on blood flow.

  • Function: Arteries carry blood away from the heart, while veins return blood to the heart. Arteries have thicker, more elastic walls to handle the higher pressure generated by the heart’s pumping action, while veins have thinner walls but contain valves to ensure blood flows in one direction.

Capillary beds consist of two types of vessels

  • Vascular shunt - directly connects an arteriole to a venule

  • True capillaries which are exchange vessels of nutrients and gasses (oxygen and carbon dioxide)

Vital signs

Pulse - pressure wave of blood; monitored at pressure points where pulse is easily palpated; carotid pulse will have the strongest pulse

Blood pressure

  • Measurements by health professionals are made on the pressure in large arteries

    • Systolic: pressure at the peak of ventricular contraction

    • Dyastolic: pressure when ventricles relax

Blood Composition

  • Cellular Elements (Approx. 45% of blood volume):

    • Red Blood Cells (Erythrocytes): These cells contain hemoglobin (iron-containing protein), a protein that binds oxygen and transports it from the lungs to the body’s tissues. They also help carry carbon dioxide back to the lungs for exhalation.

    • White Blood Cells (Leukocytes): These are part of the immune system and help defend the body against infections and foreign invaders. They can be further categorized into several types, including lymphocytes, neutrophils, monocytes, eosinophils, and basophils, each with specific functions in immune response.

    • Platelets (Thrombocytes): These cell fragments play a crucial role in blood clotting and wound repair.

  • Plasma (Approx. 55% of blood volume):

    • Composition: Plasma is a pale yellow liquid that consists mostly of water (about 90%), but it also contains dissolved ions, proteins, nutrients, hormones, and waste products.

    • Functions:

      • Osmotic Regulation: Plasma proteins, such as albumin, help maintain osmotic pressure, which is crucial for regulating the exchange of fluids between blood and tissues.

      • Transport: Plasma serves as the medium for transporting various substances

Blood Clotting

  • the formation of a solid clot from liquid blood

  • A cascade of reactions converts inactive fibrinogen to fibrin, forming a clot.

  • A blood clot formed is called a thrombus.

Atherosclerosis, Heart Attack, and Stroke

  • Atherosclerosis is caused by the buildup of fatty deposits (plaque) within arteries

  • Cholesterol is a key player to the development of this

    • Low density lipoprotein: delivers cholesterol to cells for membrane production

    • High-density lipoprotein: scavengers excess cholesterol for return to the liver

  • Heart Attack or myocardial infarction is the damage or death of cardiac muscle resulting from blockage of one or more arteries.

  • Stroke is the death of a nervous tissue in the brain resulting from the rupture or blockage of arteries in the head.

  • Angina pectoris is the chest pain caused by partial blockage of the coronary arteries.

Respiratory System

  • supplies O2 for cellular respiration and disposes CO2

  • Partial pressure

    • the pressure exerted by a particular gas in a mixture of gasses

    • also apply to gases dissolved in liquids such as water

  • Gasses undergo net diffusion from a region of higher partial pressure to lower partial pressure

Respiratory media

  • in a given volume, there is less O2 available in water than in air

  • Obtaining O2 from water requires greater efficiency than air breathing.

Respiratory surfaces

  • animals require large, moist, respiratory surfaces for exchange of gasses between their cells and the respiratory medium, either air or water.

  • Gas exchange across respiratory surfaces take place by diffusion. these can vary in animals and include, skin, gills, lungs, tracheae

Gills in Aquatic animals

  • large outfoldings of the body that create a surface area for gas exchange

  • Fish gills use a concurrent exchange system where blood flows in the opposite direction of water passing over the gills.

Ventilation - moves the respiratory medium over the respiratory surface

Tracheal systems in insects

  • consists of a network of branching tubules throughout the body

  • respiratory and circulatory systems are separate.

  • Larger insects must ventilate their tracheal system to meet O2 demands

Lungs

  • unfolding of the body surface

  • the circulatory system transports gasses between the lungs and the rest of the body

  • the size and complexity of lungs correlate with an animal’s metabolic rate.

  • A system of branching ducts conveys air to the lungs

    • nostrils: where air is inhaled, filtered, warmed, humidified, and sampled for odors

    • pharynx: directs air to the lungs and food to the stomach; throat

    • swallowing moves the larynx upwards and tips the epiglottis over the glottis in the pharynx.

  • Air passes through the pharynx, larynx, bronchi, and bronchioles to the alveoli where gas exchange occurs

  • exhaled air passes over the vocal cords in the larynx to create sounds

  • cilia and mucus line of the air ducts and move particles up to pharynx

Alveoli

  • oxygen diffuses through the moist film of the epithelium and into the capillaries

  • Carbon dioxide diffuses from the capillaries across the epithelium into the air space

  • Surfactants

    • secretions that coat the surface of the alveoli

    • preterm babies lack surfactant

Breathing

  • the process that ventilates the lungs

  • inhalation and exhalation of air

How amphibians breathe

  • an amphibian such as frog breathe by positive pressure breathing, which forces air down the trachea

How a bird breathes

  • birds have eight or nine air sacs

    • functions as bellows that keep air flowing through the lungs

  • Air passes through lungs in one direction only

  • passage of air through the entire system requires two cycles of inhalation and exhalation

  • highly efficient

How a mammal breathes

  • negative pressure breathing - pulls air into lungs

  • lung volume - increases as the rib muscles and diaphragm contract

  • tidal volume - the volume of air inhaled with each breath

  • vital capacity - the maximum tidal volume

  • Residual volume - air that remains in the lungs after exhalation

Control breathing in humans

  • usually regulated by involuntary mechanisms

  • medulla oblongata of the brain

    • where breathing centers are found

    • regulated the rate and depth of breathing in response to pH changes in the cerebrospinal fluid

    • when co2 increases (in strenuous activity) blood pH falls

Respiratory pigments

  • proteins that transport oxygen greatly increase the amount of oxygen blood can carry

  • Arthropods and many molluscs have hemocyanin with copper as the oxygen binding component.

  • Most vertebrates use hemoglobin and is contained in the erythrocytes

    • a single hemoglobin can carry 4 molecules of O2

    • The hemoglobin dissociation curve shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O2

    • hemoglobin plays a minor role in the transport of CO2 and assists buffering the blood

Excretory System and Urine Formation

  • Osmoconformers - consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity.

  • Osmoregulators - expend energy to control water uptake and loss in a hyperosmotic to hypoosmotic environment

Transport epithelia in osmoregulation

  • epithelial cells specialized for moving solutes in specific directions

  • typically arranged into complex tubular networks

An animal’s nitrogenous wastes reflect its phylogeny and habitat

Animals excrete nitrogenous wastes in different forms: ammonia, urea, and uric acid (order from most toxic to least toxic).

Energy expenditure → uric acid > urea > ammonia

Excretory Process

Excretory systems

  • regulate movement between internal fluids and the external environment

  • most produce urine by refining a filtrate derived from body fluids

  • key functions

    • filtration- filtering body fluids

    • reabsorption - reclaiming valuable solutes

    • secretion- adding nonessential solutes and wastes to the filtrate

    • excretion- processed filtrate containing nitrogenous wastes is released from the body

Survey of excretory systems

protonephridia

  • network of dead-end tubules connected to the external opening

  • the smallest branches of the network are capped by a cellular unit called a flame bulb

  • these tubules excrete a dilute fluid and function in osmoregulation

metanephridia

  • consists of tubules that collect coelomic fluid and produce dilute urine for excretion

  • each segment of an earthworm has a pair of open-ended metanephridia

Malpighian tubules

  • remove wastes from hemolymph in insects and other terrestrial arthropods

Kidney

  • excretory organs of vertebrates, function in both excretion and osmoregulation

Proximal Tubule:

• Reabsorbs ions, water, and nutrients.

• Descending Limb of the Loop of Henle:

• Reabsorbs water through aquaporin channels.

• Driven by the high osmolarity of interstitial fluid, which is hyperosmotic to the filtrate.

• Filtrate becomes more concentrated as water is reabsorbed.


• Ascending Limb of the Loop of Henle:

• Salt (NaCl) is reabsorbed, but water is not.

• Filtrate becomes dilute as salt leaves.

• Distal Tubule:

• Regulates potassium (K⁺) and sodium chloride (NaCl) concentrations in body fluids.

• Controls pH by moving ions (H⁺ and HCO₃⁻).


• Collecting Duct:

• Carries filtrate to the renal pelvis.

• Reabsorbs water and solutes, concentrating urine.

• Urine is hyperosmotic relative to body fluids.

Concentrating Urine in the Mammalian Kidney

• Loop of Henle:

• In the descending limb, water leaves by osmosis, concentrating solutes.

• NaCl diffuses out of the ascending limb, maintaining high osmolarity in the renal medulla.

• Countercurrent Multiplier System:

• Maintains a high salt concentration in the kidney, crucial for water reabsorption and urine concentration.