Human Physiology Week 1 - Cell Injury Study Guide

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Questions and Answers

Which of the following best describes the role of fibroblasts in connective tissue?

They produce energy through ATP.

They store nutrients for muscle cells.

They transmit electrical impulses for communication.

They produce collagen and elastin for tissue structure. (correct)

What is a consequence of excessive production of reactive oxygen species (ROS)?

Reduced inflammation in tissues.

Oxidative stress leading to cell injury. (correct)

Increased ATP production.

Enhanced cellular repair mechanisms.

Which type of muscle tissue is under voluntary control?

Cardiac muscle.

All types of muscle tissue.

Skeletal muscle. (correct)

Smooth muscle.

Which of the following factors does NOT influence the reversal of cellular injury?

Patient's age. Signup and view all the answers

What occurs during the process of hypertrophy?

Increase in the size of cells. Signup and view all the answers

What is the primary role of antioxidants in relation to reactive oxygen species?

Neutralize ROS to prevent cell damage. Signup and view all the answers

Which response is NOT typically associated with chronic cellular stress?

Cellular death. Signup and view all the answers

What is the correct order of the hierarchy of tissue organization?

Chemical level, Cellular level, Tissue level, System level Signup and view all the answers

Which of the following accurately describes the extracellular matrix?

Fluids and molecules secreted by cells that affect the structure and function of the tissue Signup and view all the answers

Which of the following is NOT a function of epithelial tissue?

Lies beneath muscle tissue Signup and view all the answers

What role does collagen play in the extracellular matrix?

Provides structure and strength Signup and view all the answers

Which component of the extracellular matrix is responsible for providing tissue elasticity?

Elastin Signup and view all the answers

How do proteoglycans affect tissue properties?

They fill space and help attract water, influencing tissue softness Signup and view all the answers

Which of the following is NOT a type of tissue mentioned?

Muscle tissue Signup and view all the answers

What is the main function of integrins in the extracellular matrix?

Act as the glue that connects cells to each other and to the extracellular matrix Signup and view all the answers

Study Notes

Tissue Organization

Tissues are organized in a hierarchical manner:
- Chemical level: Atoms combine to form molecules
- Cellular level: Cells are composed of various molecules.
- Tissue level: Composed of cells and their secreted extracellular matrix
- System level: Composed of different tissue types interacting to form organs and organ systems
Extracellular matrix (ECM) is secreted by cells and influences tissue structure and function.
- In bone, ECM is hard and rigid.
- In tendons, ECM is stretchy and flexible.
Key ECM molecules:
- Collagen: Provides strength and structure
- Elastin: Provides elasticity and stretchiness
- Proteoglycans: Fill space and attract water, determining tissue "softness" (e.g., cartilage).
- Integrins: "Glue" that connects cells to each other and to other ECM proteins.

Tissue Types

Epithelial tissue:
- Functions: Protection, lining of organs, glandular secretion.
- Examples: Skin, cornea, lining of blood vessels and intestines.
Connective tissue:
- Functions: Space filling, structural support, energy storage.
- Examples:
  - Connective tissue proper (e.g., areolar tissue)
  - Blood
  - Cartilage
  - Bone
  - Ligaments
  - Tendons.
- Fibroblasts are important for connective tissue:
  - Produce collagen, elastin, etc.
  - Involved in tissue healing and repair.
Muscle tissue:
- Functions: Contraction to produce movement.
- Types:
  - Skeletal (voluntary control)
  - Smooth (involuntary control, lining organs)
  - Cardiac (heart muscle)
Nervous tissue:
- Functions: Transmission of electrical impulses for information transfer.

Cell Injury and Adaptation

Factors influencing cell injury reversal:
- Mechanism of injury
- Duration of injury
- Severity of injury
Free radical theory of cellular injury:
- Reactive oxygen species (ROS) are oxygen molecules with unpaired electrons.
- ROS can react with various molecules and form toxic chemicals, damaging cells and pathogens.
- Excess ROS production is called "oxidative stress" implicated in many disease processes.
- Oxidative stress can be caused by various factors like excessive exercise, radiation, tobacco smoke, and heat.
Antioxidants neutralize ROS, preventing DNA and cell damage.
- Endogenous antioxidants (e.g., glutathione, peroxidase, catalase) are produced by the body.
- Exogenous antioxidants (e.g., Vitamin C, E, beta-carotene) are obtained from the diet.
Exercise and free radicals:
- Exercise increases ROS formation acutely.
- This can impair muscle force production, but also triggers adaptive responses to increase endogenous antioxidant production and repair mechanisms.
- Excessive exercise can cause significant oxidative stress.
Genetic alterations causing cell injury/death:
- Alterations in chromosome structure or number: Examples: Down Syndrome
- Single gene mutations: Example: Sickle Cell Anemia
- Multiple gene mutations interacting with environmental factors: Examples: Type II Diabetes, Obesity.
Possible responses to physical stress:
- Decreased stress tolerance (atrophy)
- Maintenance
- Increased stress tolerance (hypertrophy, hyperplasia)
- Injury
- Death
Mechanical stressors initiating cellular response:
- Overstretch
- Compression
- Friction

Reversible Cell Injury

Increased sodium and calcium influx into the cell
Cell swelling
Impaired organelle function (especially mitochondria, leading to decreased ATP production and cellular acidosis)
Reversal is possible if:
- The nucleus remains undamaged.
- The energy source is restored.
- The toxic injury is neutralized.
Reversal leads to the cell returning to its normal state of function.

Chronic Cellular Stress Responses

Atrophy:
- Reduction in cell or organ size.
- Examples: Bone loss, muscle wasting, brain cell loss.
Hypertrophy:
- Increase in cell size due to increased functional demands or hormonal input.
- Occurs primarily in cardiac and skeletal muscle, which cannot increase cell number.
- Example: Left ventricular hypertrophy due to exercise training or hypertension.
Hyperplasia:
- Increase in cell number due to increased functional demands, hormonal stimulation, or physical stimulation.
- Often occurs alongside hypertrophy.
- Examples: Callus formation, thickened uterine wall lining, smooth muscle proliferation in diseases like obstructive airway diseases, prostate enlargement, and hypertension.
Metaplasia:
- Change in cell morphology and function, converting one cell type into another.
- Example: Ciliated pseudostratified epithelium becoming squamous epithelium in smokers.
Dysplasia:
- Increase in cell numbers with loss of morphology and tissue organization.
- Occurs in chronically injured areas undergoing hyperplasia or metaplasia.

Irreversible Cell Injury

Cell death:
- Apoptosis: Genetically mediated, programmed cell death, with no inflammatory response.
- Necrosis: Active process of degrading dead cells involving nuclear and mitochondrial damage, lysosome release, and self-digestion of dead tissue, leading to inflammatory response.
- Contents of dead cells are released into the extracellular fluid and circulation, causing inflammation.
- Removal of necrotic tissue is needed for repair or regeneration

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Description

Explore the hierarchical organization of tissues from the chemical to the system level. This quiz covers the extracellular matrix's role in various tissue types, including epithelial, bone, and tendons, and highlights key molecules like collagen and elastin.