L22 - Respiration & Excretion

What external exchange surfaces help maintain homeostasis by removing metabolic wastes, including CO₂ through gas exchange and nitrogenous wastes through excretion?

→ Respiratory system and excretory system

In this context, what are metabolic wastes and why must they be removed to maintain homeostasis?

→ Byproducts of metabolism that must be removed to keep internal conditions stable

What is defined by its thin walls ( diffusion fast), large surface area, being moist ( gasses dissolve), many blood vessels?

Respiratory system: gas exchange between organism & enviroment

What exchange system is the simplest, has high SA:vol, low metabolic rate, works in moist environments, includes platyhelminths and porifera, and does not work for large animals?

Body surface

What exchange system is used by multicellular aquatic organisms, has very high SA from outfolding of body surface, performs gas exchange in H₂O, with inner circulatory system and outer H₂O?

Gills

What exchange system involves blood and H₂O flowing in opposite directions, where at each point in the gill [O₂] in H₂O > [O₂] in blood?

→ Countercurrent exchange system

What exchange system consists of a network of branching air tubules with tracheoles as the smallest branches, where gas exchange occurs close to every cell and there is no circulatory system?

→ Tracheal system

What exchange system is used by terrestrial vertebrates, involves infolding of body surface, has no direct contact with the rest of the body, and has a circulatory system?

→ Lungs

What respiratory system includes a pair of spongy, elastic lungs located in the thoracic cavity and connected by tubes?

→ Mammalian respiration

What is the pathway of gas flow from the nasal cavity to the terminal bronchiole?

→ Nasal cavity → Pharynx → Larynx → Trachea → Primary bronchus → Secondary bronchus → Tertiary bronchus → Bronchiole → Terminal bronchiole → alveolar duct → alveolus

What structures are the location of gas exchange in the lungs, tiny air sacs, single layer epithelial cells, massive SA, and are surrounded by capillaries for gas exchange?

→ Alveoli

What process involves negative pressure breathing, where P in lungs < P outside, gas moves from high P (outside) to low P (inside), rib cage muscles contract and lift upward, diaphragm contracts and descends, thoracic cavity volume increases, and air is pulled in?

→ Inhalation

What process is passive and occurs when the rib cage and diaphragm return to resting position?

→ Exhalation

What system regulates breathing automatically?

→ Autonomic NS

What chemical change links CO₂ from cellular respiration to pH changes in blood and CSF ( cerebrospinal fluid )?

→ CO₂ + H₂O ⇌ H₂CO₃ → HCO₃⁻ + H⁺

More H+ = Low PH

Carbon dioxide mixes with water to form carbonic acid, which breaks into bicarbonate and hydrogen ions.

The hydrogen ions indicate pH level.

pH changes are detected by receptors in the medulla, which adjusts breathing

What happens when metabolic rate increases, causing CO₂ to increase and pH to decrease, leading receptors to signal the medulla and increase depth and rate of breathing?

→ CO₂ excreted

What process maintains electrolytes and H₂O in body fluids across membranes?

→ Osmoregulation

In terrestrial vertebrates, what makes H₂O loss critical and how is H₂O replaced?

→ H₂O loss: lungs, skin, digestion, urine; H₂O replacement: drink, eat moist food, metabolism

What adaptations reduce H₂O loss?

body coverings, nocturnal behavior, and concentrated urine:

Nocturnal behavior: Desert: decrease temperature, increase humidity, decrease evaporative water loss

Human urine is 4x concentrated in blood

Desert animals > 20x

In humans, what is the main osmoregulatory organ?

→ Kidneys

What process involves removal of metabolic waste to maintain homeostasis, including removal of CO₂ by the respiratory system?

→ Excretion

What waste results from proteins → amino acids and nucleic acids → nitrogenous bases, involves deamination (removal of NH₂), forms NH₃, and must be excreted because it is very toxic?

→ Nitrogenous waste

What type of nitrogenous waste is very soluble in H₂O, quickly diffuses out, has no toxic buildup, and requires very little metabolic energy?

→ NH₃ (ammonia)

For Inverts + aquatic animals

What type of nitrogenous waste is the #1 nitrogen waste of humans, synthesized in the liver from NH₃ and CO₂, has very low toxicity, and requires energy for production and H₂O for excretion?

→ Urea

What kind of nitrogenous waste is produce very little by humans, has 15 step process in the liver, non- toxic, very insoluble, and forms a semisolid paste with feces?

( pigeons, insects, reptiles)

→ Uric acids

What organ adjusts composition in blood, maintains internal chemical balance, constantly filters material from blood, and produces urine?

Kidney

What structure is present at ~1 million in each kidney?

→ Nephron

What structures make up the nephron structure?

1. Bowman's capsule,

2. glomerulus

3. proximal convoluted tubule

4. loop of Henle (descending & ascending)

5. distal convoluted tubule

6. collecting duct

What processes in urine production include H₂O and solutes forced from blood into nephron (filtrate), valuable substances reclaimed from filtrate and returned to body fluids, other substances added to filtrate, and filtrate (urine) leaving the system and body?

→ Filtration, reabsorption, secretion, excretion

What is the pathway of urine from kidney to exit of the body?

→ Kidney → ureter → bladder → urethra