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Chapter 40
Introduction to Animal
Structure & Function
Tissue
a) 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 methods
Stages of food 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 marrow
T 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 defense
B 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 defense
T-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
Adaptations
1) 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 mechanisms
1) 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 mechanisms
tubular 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
Nephron
a) 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 pastelike urine of land snails, insects, birds, reptiles
*reproductive mode of terr. animals is related to Nwaste form