Chapter 40Introduction to Animal Structure & Function

Tissuea) epithelial – cover exterior & lines organs & cavities (barrier- tightly packed)

b) connective – bind & support other tissues ex: loose, adipose, fibrous, cartilage, bone, blood

c) nervous – transmit electrical impulses

d) muscle – long, excitable cells with parallel microfilaments *most abundant in animals

Homeostasis

• maintaining internal balance

• negative feedback – reaction to shifts in

variations that reverse mechanisms

• positive feedback – triggers mechanisms to amplify rather than reverse the change

Bioenergetics

-exchange of energy with the environment

-minimum metabolic rates for endotherms are generally higher than for ectotherms

-rate is inversely related to body size

Chapter 41

Animal Nutrition

•Heterotrophic by a variety of methodsStages of good processing:

a) ingestion – 1st stage; act of eating

b) digestion – enzymatic breakdown of food into monomers for absorption

*must occur in specialized compartment where hydrolytic enzymes can attack food molecules without damaging the animal’s own cells

c) absorption – uptake of nutrients by body cells

d) elimination – passage of undigested materials out of the body in feces

Intracellular digestion

Food particles

engulfed &

digested in

vacuoles

Extracellular digestion

In gastrovascular cavity or alimentary canal

alimentary canal

• complete with two openings

mouth pharynx – esophagus crop

gizzard intestine anus

Mammalian digestive system

• 1-way tract; separated by sphincters

• peristalsis moves material through

• accessory glands that add to tract via ducts:

salivary glands

pancreas

liver (stores bile in gall bladder)

1) oral cavity –site of mechanical digestion & start of chemical digestion

• >1L of saliva secreted each day

• Contains mucin (glycoprotein) & amylase

(hydrolytic enzyme)

• bolus – ball of food; pushed to pharynx to be swallowed

2) esophagus – carries by peristalsis to stomach

-cardiac sphincter

3)stomach – stores food & grinds; secretes gastric juice (~3L per day)

4)small intestine - >6m in humans; most

digestion & almost all absorption

*1st 25cm duodenum, jejunum, ileum – absorb; great surface area due to villi & microvilli with blood vessels

*liver – secretes bile to emulsify fats

*pancreas – secretes digestive enzymes (zymogens) – breakdown proteins

-Ileocecal valve

5) large intestine (colon) – reabsorbs water;

cecum with appendix

6) rectum – terminal part of colon

-2 anal sphincters – 1 voluntary & 1 involuntary

Vertebrate digestive system• dentition dictates diet

• herbivores – longer alimentary canals with specialized chambers where symbionts digest cellulose

• diet – carbohydrates –stored as glycogen, fats (in adipose tissue) are fuel

• vitamins & minerals necessary cofactors for enzyme action

Chapter 42

Circulation & Gas Exchange

• O2, CO2, nutrients & metabolic waste exchange across fluid bathed membranes

• diffusion is too slow to all cells, so transport system is necessary

• Invertebrates: gastrovascular cavity (Cnidarians,flatworms)

*circulatory system (open or closed)

• Vertebrates: closed system with blood vessels & 2-4 chambered heart

*capillaries connect arterioles & venules

*veins – carry blood back to heart

*arteries – carry blood away from heart

-1 way flow with valves

**pulmonary circulation – to/from lungs

**cardiac – through heart

**systemic – to/from body

• heart rate (pulse) determines cardiac output –

volume of blood pumped into systemic circulation per minute, which determines pressure

• coordinated by conduction system in sinoatrial (SA) node (pacemaker) – initiates wave of contraction that spreads to both atria,hesitates at atrioventricular (AV) node, then to both ventricles

• capillary exchange – substances traverse epithelium by diffusion or are dissolved in fluids & forced out by blood pressure at atrial end

Blood• Suspension of cells in plasma (~90% water)

• ~4-6L of blood on avg.

• pH of ~7.4

• RBC (erythrocytes) ~25 trillion in blood

-transport O2 (RBC & WBC produced in red bone marrow)

• WBC (leukocytes) 5 types

-phagocytize bacteria & debris & produce antibodies

• platelets – fibrinogen allows clotting

Respiration• gills – aquatic

• tracheae – insects

• lungs – most terrestrial vertebrates – enclosed in double walled sac

• nose/mouth – inhale air to pharynx

• trachea – transports air to lungs; branches into bronchi bronchioles alveoli

• epiglottis covers opening to trachea (glottis)

• negative pressure breathing in mammals

Weddell seal

Chapter 43

The Body’s Defenses

Lymphatic system

• Returns fluid to blood & aids in body defense; nodes help fight infection

Nonspecific defense (general)

1) skin/mucus membranes – 1st line

2) phagocytes (macrophages) – 2nd line

complement (group of ~20 proteins)

• Inflammatory response:

*prostaglandin – increases blood flow

*histamines – cause vasodilation

Specific defense• Humoral immunity – cells (lymphocytes) stimulated to secrete antibodies

B cells – proliferate in bone marrowT cells – mature in the thymus

*both come from stem cells in the bone marrow & recognize specific pathogens

antigens – foreign molecules that elicit a response by lymphocytes & are recognized by B & T cells

antibodies – soluble proteins secreted by B cells during an immune response

Specific defenseB or T cell activation occurs when an antigen

binds to a B or T cell

The lymphocyte forms 2 clones of cells in a process called clonal selection,resulting in

thousands of cells, all specific to this antigen.

effector cells combat the antigen

memory cells (long-lived) bear receptors for

the same antigen allowing them to quickly

mount an immune response in subsequent

infections

Specific defenseT-cell receptors bind antigens that are displayed

by antigen-presenting cells (APCs) on their MHCs (major histocompatibility complex)-

proteins that are the product of a group of genes

Specificity of B & T cells is a result of shuffling &

recombination of several gene segments & results in >1million different B cells & 10 million

different T cells, ea. responding to only 1 antigen

Specific defense

Cytotoxic T cells destroy body cells that are infected by a pathogen or cancer cells

Helper T cells activate both B and T cells

Chapter 44

Regulating the Internal Environment

Adaptations1) body insulation

2) vasodilation/vasoconstriction

3) countercurrent heat exchangers

4) panting, sweating, bathing

5) liver has multiple functions in homeostasis

Torpor

• Physiological state characterized by decrease in metabolism, heart, respiratory rates; enables temperatures withstanding varying unbearable temperatures or absences of food/water

• ex: aestivation (summer torpor) & hibernation

Osmoregulatory mechanisms1) transport epithelia – single sheet of cells facing

ext. env. or some channel that leads to exterior

through an opening on body’s surface; transports

salt followed by osmotic flow of water

Osmoregulation• Balance is essential• Requires mechanisms of osmoregulation

2 basic:

1) osmoconformers (most marine inverts.) – marine animals that are isotonic with their

SW environments; do no actively adjust

2) osmoregulators (most marine verts.) –

animals whose body fluids are not isotonic with ext.

env.; either discharge or take in water in hypertonic

env.

Adaptations• FW organisms:

-take in H2O from hypotonic env. by contractile vacuoles (in Protozoa); excrete lots of dilute urine

• Terrestrial animals:-protect against desiccation by drinking & eating high content water foods & by hormonal & nervous control of thirst, behavioral adaptations & excretory organs that conserve water

Osmoregulatory mechanismstubular systems –

a) protonephridia (in flatworms) - network of

closed tubes lacking internal openings &

capped by flame bulbs – excrete dilute fluid

b) metanephridia – internal openings that collect

body fluids (in most annelids) – pump out salt for

reabsorption & dilute urine is excreted

c) Malpighian tubules – remove nitrogenous

waste from hemolymph – produce dry waste matter

Kidney

• compact organ with many excretory tubules

• consisting of nephrons & collecting ducts associated blood vessels

Nephrona) Bowman’s capsule – surrounds ball of capillaries

called glomerulus

b) Proximal tubule

c) Loop of Henle

d) Distal tubule

*collecting duct gets fluid from several nephrons &

passes urine to kidney’s central receptacle (renal

pelvis); urine carried by ureter to urinary bladder

• Kidney’s transport epithelia regulate blood composition• Nephrons control is through:

a) filtration - blood pressure nonselectively filters water & small solutes from glomerulus into lumen of

nephron tubule

b) secretion – additional substances destined for excretion are directly secreted from interstitial fluid into

tubule by active & passive transport

c) reabsorption – filtered substances that must be returned to blood, such as vital nutrients & water are reabsorbed from filtrate at various points along nephron

• Most salt & water filtered from blood is reabsorbed by proximal tubule; NH3, drugs, H+ are selectively secreted into filtrate; glucose & AA’s actively transported out of filtrate; K+ reabsorbed

Mammalian kidney• terrestrial adaptation• water-conserving• collecting duct carries filtrate through medulla; water

exits by osmosis• urea diffuses out of tubule, joining salt in forming

osmotic gradient enabling kidney to produce urine hypertonic to blood

• regulation varies as it moves through nephron• produces 2 solute gradients making hypertonic urine• body’s hydration needs determine osmoregularity of

urine

• ADH (antidiuretic hormone) – released in response to rise in blood osmolarity signaled by osmoreceptor cells in hypothalamus, triggering increased water reabsorption by tubule

• JGA (juxtaglomerular apparatus) – responds to decreased blood pressure or blood volume by releasing renin triggering formation of angiotensin II (peptide) causes vasoconstriction & releases aldosterone stimulating reabsorption of Na+ & passive flow of H2O from filtrate

Adaptations• Excretion of N wastes are secondary function of

kidney through evolution

• NH3 excreted as:

1) NH3 in most aquatic animals through gills or

ext. surfaces

2) urea (less toxic) – converted by liver in mammals

& amphibians, excreted in conc. forms with

minimal water loss

3) uric acid – insoluble precipitate, excreted in paste-

like urine of land snails, insects, birds, reptiles

*reproductive mode of terr. animals is related to N-waste form