Animal Structure

Animal Structure & Function

1. Key Definitions

• Diffusion: Movement of substances from where there’s more to less. Example: oxygen moving into blood.

• Diffusion Gradient: The difference in concentration that makes diffusion happen.

• Inhalation: Breathing in; lungs fill with air as the diaphragm moves down.

• Exhalation: Breathing out; air leaves as the diaphragm moves up.

• Coronary: Related to the heart’s blood vessels (e.g., coronary arteries).

• Cardiac: Anything to do with the heart (e.g., cardiac muscles).

• Ulcer: A sore, often caused by stomach acid.

• Asthma: Narrowed airways making it hard to breathe.

• Constipation: When stool becomes hard or slow to pass.

2. Digestive System: A complex system that processes food, absorbs nutrients, and eliminates waste.

What Happens Where

Mouth

• Processes food through chewing, which mechanically breaks down food into smaller pieces, increasing the surface area for enzyme action.

• Saliva, produced by salivary glands, contains the enzyme amylase that begins the chemical breakdown of carbohydrates into simpler sugars. This initial digestion aids in the tasting of food and lubricates it for easier swallowing.

Stomach

• The stomach further churns the food, mixing it with gastric juices that consist of hydrochloric acid and digestive enzymes (like pepsin).

• The acidic environment kills bacteria and denatures proteins, which allows enzymes to efficiently break down proteins into smaller peptides. This mixture forms a semi-liquid substance known as chyme, which is eventually released into the small intestine.

Small Intestine

• The small intestine is the primary site for nutrient absorption and extends approximately 20 feet in humans. It includes three sections: the duodenum, jejunum, and ileum.

• The walls of the small intestine are lined with villi and microvilli that significantly increase the surface area for enhanced absorption of nutrients into the bloodstream.

• Digestive enzymes from the pancreas and bile from the liver continue the breakdown of carbohydrates, proteins, and fats into absorbable forms.

Large Intestine

• After nutrients are absorbed, the remaining undigested food passes into the large intestine, which is about 5 feet long.

• The primary function here is to absorb water and electrolytes, transforming the liquid waste into solid stool. Beneficial bacteria present in the large intestine also assist in fermenting unabsorbed material, contributing to vitamin production, particularly Vitamin K and certain B vitamins.

Rectum/Anus

• The rectum serves as a temporary storage site for feces before expulsion. When it is full, nerve signals trigger the urge to defecate. The anus features sphincter muscles that allow control over the expulsion of waste, ensuring it occurs at an appropriate time.

  

Nutrients Breakdown Helpers

• Carbohydrates → Sugar:

  • Amylase in saliva and pancreatic secretions breaks down complex carbohydrates into simple sugars, providing quick energy sources for the body.

• Proteins → Amino acids:

  • Stomach enzymes degrade protein structures, producing amino acids that are crucial for numerous body functions, such as building and repairing tissues, and supporting immune function.

• Fats → Fatty acids:

  • Bile from the liver emulsifies fats, allowing lipases from the pancreas to convert

• Nutrients Breakdown Helpers:

  • Carbohydrates → Sugar (amylase in saliva/pancreas).

  • Proteins → Amino acids (stomach enzymes).

  • Fats → Fatty acids (bile from liver).

3. Circulatory System → Transports nutrients and oxygen to cells (via blood vessels and heart).

Pathway of Blood

1. Oxygen-Rich Blood from the Heart: Blood is pumped from the left ventricle of the heart into the aorta, the body's main artery. This oxygen-rich blood is then distributed through a network of arteries that branch out throughout the body, reaching various organs and tissues.

2. Delivery of Oxygen and Nutrients: As blood travels through the arteries, it delivers essential oxygen and nutrients to all the body’s cells. Oxygen is crucial for cellular respiration, which produces the energy necessary for cell survival and function. Alongside oxygen, nutrients such as glucose, vitamins, and minerals also circulate in the blood, providing cells with what they need for growth, repair, and metabolic processes.

3. Waste Collection: While delivering oxygen and nutrients, blood picks up waste products created by cells during metabolic processes, including carbon dioxide, urea, and other toxins that need to be removed from the body to maintain homeostasis.

4. Return to the Heart: After circulating through the body, the oxygen-poor blood, which is now enriched with carbon dioxide and other waste materials, returns to the heart through the veins. This journey typically begins with smaller venules that merge into larger veins, ultimately leading to the superior and inferior vena cavae, which empty into the right atrium of the heart.

5. Lungs for Oxygenation: Once in the right atrium, blood flows into the right ventricle, which pumps it into the pulmonary arteries. These arteries transport the blood to the lungs, where carbon dioxide is exchanged for fresh oxygen. In the lungs, blood travels through the capillaries surrounding the alveoli (tiny air sacs), allowing for efficient gas exchange.

6. Completion of the Cycle: Oxygen-rich blood then returns to the heart via the pulmonary veins, entering the left atrium and completing the circulation cycle. This oxygen-rich blood is then ready to be pumped out again to supply the body, highlighting the continuous nature of the circulatory process.

What Blood Transports

Blood serves several critical functions in the body, primarily through the transport of various substances vital for cellular function and overall homeostasis. The key components of blood transport include:

1. Oxygen to Cells:

   • Blood transports oxygen from the lungs, where it is picked up during the inhalation process, to all the body's cells. This oxygen is essential for cellular respiration, a metabolic process that produces energy (ATP) from glucose. The oxygen binds to hemoglobin in red blood cells, allowing for efficient transport. Excess carbon dioxide produced as a waste product of cellular respiration is also carried back to the lungs.

2. Carbon Dioxide to Lungs:

   • Carbon dioxide, a byproduct of metabolism, is transported from the tissues back to the lungs for exhalation. This process is crucial for maintaining the body’s acid-base balance (pH levels), as high levels of carbon dioxide can lead to respiratory acidosis. The transport occurs primarily in plasma and within red blood cells, where it binds to hemoglobin or is converted to bicarbonate ions.

3. Nutrients from Digestion to Cells:

   • Nutrient-rich blood from the digestive tract is carried to the liver for processing and then distributed to cells throughout the body. This includes carbohydrates (in the form of glucose), proteins (as amino acids), and lipids (fatty acids). These nutrients are essential for growth, repair, and maintenance of body tissues, as well as energy production.

4. Waste to Kidneys:

   • Blood also plays a critical role in waste management by transporting waste products (such as urea, creatinine, and excess salts) to the kidneys. The kidneys filter these wastes from the blood, which are then excreted from the body through urine. This removal of waste is essential for preventing toxicity and maintaining fluid and electrolyte balance in the body.

4. Respiratory SystemThe respiratory system is responsible for the exchange of gases, primarily oxygen and carbon dioxide, between the body and the environment, facilitating cellular respiration and maintaining the body's pH balance.

Inhalation

• Process: During inhalation, air is drawn into the lungs through the nose or mouth. The diaphragm, a dome-shaped muscle below the lungs, contracts and moves downward, creating a vacuum that pulls air into the lung's airways. This intake of air fills the lungs, specifically reaching alveoli, which are tiny air sacs where gas exchange takes place.

• Oxygen Movement: As the air enters the alveoli, oxygen molecules move across the thin alveolar walls into the surrounding capillaries. This movement occurs due to a concentration gradient, where the oxygen concentration is higher in the alveoli than in the blood, facilitating diffusion into the bloodstream.

Exhalation

• Process: Exhalation is the process of breathing out. During this phase, the diaphragm relaxes and moves upward, reducing the space in the chest cavity. This increased pressure forces air, primarily composed of carbon dioxide, out of the lungs.

• Gas Exchange: The carbon dioxide, which is a waste product of cellular metabolism that has accumulated in the blood, leaves the blood in the capillaries, passes through the alveolar walls, and is expelled from the body through the respiratory tract.

Diffusion in Capillaries

• Mechanism: The process of diffusion continues in the capillaries, which are small blood vessels that facilitate the exchange of gases and nutrients. Regarding oxygen, it diffuses from the alveoli into the blood within the capillaries, entering red blood cells where it binds to hemoglobin, the protein responsible for transporting oxygen throughout the body.

• Carbon Dioxide Transfer: Conversely, carbon dioxide diffuses from the blood (where its concentration is higher due to metabolic activity in the cells) into the alveoli to be expelled from the body. This exchange of gases is crucial for maintaining proper oxygen levels and removing carbon dioxide to ensure homeostasis in the body.

  

Diffusion in Capillaries

• Oxygen Diffusion: Oxygen molecules, once inhaled and reaching the alveoli in the lungs, have a relatively higher concentration compared to the surrounding capillaries filled with oxygen-poor blood. This difference in concentration triggers diffusion, where oxygen passes through the thin walls of the alveoli and enters the blood within the capillaries. The oxygen then binds to hemoglobin molecules in red blood cells, forming oxyhemoglobin, which is essential for transporting oxygen to tissues throughout the body.

• Carbon Dioxide Transfer: Conversely, carbon dioxide, produced as a byproduct of cellular metabolism, is carried back to the lungs by the blood in the capillaries. In the tissues, carbon dioxide concentration is higher than in the alveoli, prompting it to diffuse from the blood into the alveoli for expulsion. This gas exchange is vital for maintaining the body’s pH balance and ensuring effective respiratory function, as excess carbon dioxide can lead to respiratory acidosis if not expelled efficiently.

5. Disorders & Technologies

• Digestive: Ulcers (diagnosed by endoscopy).

• Circulatory: Heart disease (diagnosed with ECG or angiography).

• Respiratory: Asthma (treated with inhalers).

6. Systems Working Together

• The digestive, circulatory, and respiratory systems interact closely, impacting overall health and disease management.

• For instance, stress-related ulcers can exacerbate heart disease symptoms, highlighting the need for a holistic approach to treatment.

Example: Digestive & Circulatory SystemsThe digestive system is responsible for breaking down food into essential nutrients through a complex process involving mechanical and chemical digestion. Food enters the mouth where it is chewed and mixed with saliva; enzymes in saliva begin to break down carbohydrates. The chewed food then travels down the esophagus to the stomach, where it is further mixed with gastric juices and enzymes that digest proteins.

Once the partially digested food reaches the small intestine, it is exposed to bile from the liver, which emulsifies fats, and pancreatic enzymes that continue the breakdown of carbohydrates and proteins. This process allows nutrients to be absorbed through the intestinal walls into the bloodstream.

The circulatory system plays a crucial role by transporting these absorbed nutrients from the small intestine to various cells throughout the body. It utilizes a network of blood vessels: arteries carry oxygen-rich blood from the heart to the tissues, and veins return oxygen-poor blood back to the heart. Adequate circulation ensures that cells receive the necessary nutrients for energy, growth, and repair. Additionally, the circulatory system helps remove waste products produced by cells, linking the digestive outputs to the overall metabolic function of the body.