Anatomy & Physiology: Comprehensive Study Guide for Units One and Two

Histology and Anatomical Orientation

Definition of Histology

Histology is the study of the microscopic structure of tissues. It involves examining cells and tissues under a microscope to understand their structure and function within the body.

• Application: Used in medical diagnosis and research to identify tissue abnormalities.

Anatomically Correct Position

The anatomical position is a standard reference posture used in anatomy to describe locations and relationships of body parts. In this position:

• The body stands upright.

• Feet are slightly apart and facing forward.

• Arms are at the sides with palms facing forward.

• Head and eyes are facing forward.

Necessary Life Functions

Organisms must perform several essential functions to maintain life:

• Growth: Increase in size and number of cells.

• Responsiveness: Ability to sense and respond to stimuli (e.g., withdrawing hand from heat).

• Movement: Includes movement of the body, organs, cells, and substances within the body.

• Metabolism: All chemical reactions in the body.

• Reproduction: Production of offspring or new cells.

• Excretion: Removal of wastes.

• Digestion: Breakdown of food for absorption.

• Maintaining boundaries: Separation between internal and external environments (e.g., skin).

Homeostasis and Feedback Mechanisms

Definition of Homeostasis

Homeostasis is the maintenance of a stable internal environment despite changes in the external environment. It is vital for normal body functioning and survival.

Positive vs. Negative Feedback

• Negative Feedback: The response reduces or shuts off the original stimulus. Example: Regulation of body temperature, blood glucose levels.

• Positive Feedback: The response enhances or exaggerates the original stimulus. Example: Blood clotting, labor contractions during childbirth.

Components of Feedback Systems:

• Receptor: Detects changes (stimuli).

• Control Center: Processes information and determines response.

• Effector: Carries out the response to restore balance.

Cellular Structure and Function

Complexity of Organisms

Organisms are organized in a hierarchy:

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organism

ATP and Its Function

Adenosine triphosphate (ATP) is the primary energy carrier in cells. It stores and supplies energy for many biochemical cellular processes.

• Function: Provides energy for muscle contraction, nerve impulse propagation, and chemical synthesis.

• Equation:

$\text{ATP} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

Cell Connections

• Tight Junctions: Seal adjacent cells to prevent passage of molecules (e.g., in the intestines).

• Desmosomes: Anchor cells together, providing mechanical stability (e.g., skin, heart).

• Gap Junctions: Allow communication between cells via ions and small molecules (e.g., cardiac muscle).

Osmosis

Osmosis is the diffusion of water across a selectively permeable membrane from an area of lower solute concentration to higher solute concentration.

• Example: Water movement into and out of cells.

Active vs. Passive Transport

• Passive Transport: Movement of substances across membranes without energy input. Examples: Diffusion, osmosis, facilitated diffusion.

• Active Transport: Movement of substances against their concentration gradient, requiring energy (ATP). Examples: Sodium-potassium pump, endocytosis.

Transcription and Translation

• Transcription: Process of copying DNA to messenger RNA (mRNA); occurs in the nucleus.

• Translation: Process of synthesizing proteins from mRNA; occurs in the cytoplasm at ribosomes.

Cell Cycle: Interphase and Mitosis

• Interphase: Cell grows and DNA replicates; includes G1, S, and G2 phases.

• G1 Phase: Cell growth and normal functions.

• S Phase: DNA replication.

• G2 Phase: Preparation for mitosis.

• Mitosis: Division of the nucleus; includes:

  • Prophase: Chromosomes condense, spindle forms.

  • Metaphase: Chromosomes align at the cell equator.

  • Anaphase: Sister chromatids separate to opposite poles.

  • Telophase: Nuclear envelopes reform.

  • Cytokinesis: Division of the cytoplasm, forming two daughter cells.

Macromolecules

• Carbohydrates: Provide energy; examples include glucose and starch.

• Lipids: Store energy, form cell membranes; examples include fats and oils.

• Proteins: Perform structural, enzymatic, and regulatory functions; made of amino acids.

• Amino Acids: Building blocks of proteins.

Tissues and Their Types

• Epithelial Tissue: Covers body surfaces and lines cavities; functions in protection, absorption, secretion.

• Connective Tissue: Supports, binds, and protects organs; includes bone, blood, cartilage, adipose.

• Nervous Tissue: Conducts electrical impulses; found in brain, spinal cord, nerves.

• Muscle Tissue: Produces movement; includes skeletal, cardiac, and smooth muscle.

Nervous vs. Hormonal Control

• Nervous Control: Fast, short-lived responses via electrical impulses (e.g., reflexes).

• Hormonal Control: Slower, longer-lasting responses via hormones released into the bloodstream (e.g., growth, metabolism).

Integumentary System

Function of Sebaceous Glands

Sebaceous glands secrete sebum (oil) into hair follicles and onto the skin surface. Sebum lubricates and waterproofs the skin and hair, and has antibacterial properties.

Nervous System

Central Nervous System (CNS)

The central nervous system consists of the brain and spinal cord. It processes information and coordinates activity throughout the body.

Muscle Tissue Types and Function

• Skeletal Muscle: Voluntary, striated, attached to bones; responsible for body movement.

• Cardiac Muscle: Involuntary, striated, found only in the heart; pumps blood.

• Smooth Muscle: Involuntary, non-striated, found in walls of hollow organs (e.g., intestines, blood vessels); moves substances through the body.

Calcium Storage in Skeletal Muscle

Calcium is stored in the sarcoplasmic reticulum of skeletal muscle cells. Release of calcium triggers muscle contraction.

Creatine Phosphate in Muscle

Creatine phosphate serves as a rapid source of energy for regenerating ATP during short bursts of intense muscle activity.

• Equation:

$\text{Creatine~phosphate} + \text{ADP} \rightarrow \text{Creatine} + \text{ATP}$

Muscle Contraction

Muscle contraction occurs via the sliding filament theory:

• Myosin heads bind to actin filaments, pulling them inward.

• ATP is required for myosin head detachment and re-cocking.

• Calcium ions enable binding by exposing active sites on actin.

Muscle Fatigue

Muscle fatigue is the decline in ability of a muscle to generate force, often due to depletion of ATP, accumulation of lactic acid, or ionic imbalances.

Skeletal System

Parts of Bone and Their Functions

• Diaphysis: Shaft of a long bone; provides strength.

• Epiphysis: Ends of long bones; site of red bone marrow and joint articulation.

• Medullary Cavity: Central cavity containing yellow marrow (fat storage).

• Periosteum: Outer covering; contains nerves and blood vessels.

• Endosteum: Lines the medullary cavity.

Osteoporosis

Osteoporosis is a condition characterized by decreased bone mass and density, leading to fragile bones and increased fracture risk.

Healing Stages of a Simple Fracture

1. Hematoma Formation: Blood clot forms at the fracture site.

2. Fibrocartilaginous Callus Formation: Soft callus of collagen and cartilage forms.

3. Bony Callus Formation: New bone replaces the soft callus.

4. Bone Remodeling: Bone is reshaped to its original form.

Achondroplasia

Achondroplasia is a genetic disorder affecting bone growth, resulting in dwarfism due to abnormal cartilage formation at growth plates.