Anatomy & Physiology: Study Guide for Exam #2 (Cells, Tissues, Skin, Bones, Muscles, Blood, Heart, and Circulation)

Cells and Tissues

Definition and Classification of Tissues

Tissues are groups of similar cells that perform a specific function. They differ from cells (the basic unit of life) and organs (structures composed of multiple tissue types working together).

• Tissue: A group of similar cells and their extracellular products that perform a common function.

• Cell: The smallest structural and functional unit of an organism.

• Organ: A structure composed of at least two different tissue types that work together to perform specific functions.

The Four Main Tissue Types and Their Functions

• Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. Functions include protection, absorption, secretion, and sensation.

• Connective Tissue: Supports, binds, and protects other tissues and organs. Includes bone, cartilage, blood, and adipose tissue.

• Muscle Tissue: Responsible for movement. Types include skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Initiates and transmits electrical impulses to coordinate body activities.

Epithelial Tissue Structures

• Layers:

  • Simple epithelium: Single layer of cells.

  • Stratified epithelium: Multiple layers of cells.

• Cell Shapes:

  • Squamous: Flat and thin cells.

  • Cuboidal: Cube-shaped cells.

  • Columnar: Tall, column-like cells.

Connective Tissue Types and Their Roles

• Loose Connective Tissue: Supports and binds other tissues (e.g., areolar tissue).

• Dense Connective Tissue: Provides strength (e.g., tendons, ligaments).

• Cartilage: Provides flexible support (e.g., articular, costal cartilage).

• Bone: Provides rigid support and protection.

• Blood: Transports substances throughout the body.

Skin and Bones

Layers of the Skin

The skin consists of three main layers, each with distinct functions:

• Epidermis: Outermost layer; provides a waterproof barrier and creates skin tone.

• Dermis: Middle layer; contains tough connective tissue, hair follicles, and sweat glands.

• Hypodermis (subcutaneous layer): Deeper layer made of fat and connective tissue.

Parts of a Long Bone

• Diaphysis: Shaft of the bone; contains compact bone and the medullary cavity.

• Epiphysis: Ends of the bone; contains spongy bone and red marrow.

• Marrow: Soft tissue inside bones; red marrow produces blood cells, yellow marrow stores fat.

Types of Cartilage and Their Functions

• Articular Cartilage: Covers the ends of bones in joints; reduces friction and absorbs shock.

• Costal Cartilage: Connects ribs to the sternum; provides flexibility to the rib cage.

Bone Remodeling: Osteoblasts and Osteoclasts

• Osteoblasts: Cells that build new bone matrix.

• Osteoclasts: Cells that break down bone matrix.

• Bone Remodeling: The continuous process of bone formation and resorption.

Axial vs. Appendicular Skeleton

• Axial Skeleton: Consists of the skull, vertebral column, and rib cage.

• Appendicular Skeleton: Includes the limbs and girdles (shoulder and pelvic girdles).

Effects of Exercise on Bone Density

• Weight-bearing exercise increases bone density by stimulating osteoblast activity.

• Lack of exercise can lead to decreased bone mass and increased risk of osteoporosis.

Muscles and Movement

Types of Muscle Tissue

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

• Cardiac Muscle: Involuntary, striated muscle found only in the heart.

• Smooth Muscle: Involuntary, non-striated muscle found in walls of hollow organs (e.g., intestines, blood vessels).

Sarcomere Structure and Muscle Contraction

• Sarcomere: The basic contractile unit of muscle fiber.

• Actin (thin filament): Protein involved in muscle contraction.

• Myosin (thick filament): Protein that interacts with actin to produce contraction.

Muscle contraction occurs when myosin heads bind to actin, pulling the thin filaments toward the center of the sarcomere.

Voluntary vs. Involuntary Muscle Contraction

• Voluntary: Skeletal muscle contraction is under conscious control.

• Involuntary: Cardiac and smooth muscle contractions occur without conscious control.

Blood and Circulation

Blood as a Tissue

Blood is considered a connective tissue because it consists of cells suspended in a liquid extracellular matrix (plasma).

Components of Blood and Their Functions

Component	Main Function
Red Blood Cells (RBCs)	Transport oxygen and carbon dioxide
White Blood Cells (WBCs)	Defend against infection
Platelets	Assist in blood clotting
Plasma	Transports nutrients, hormones, and waste

Red Blood Cell (RBC) Maturation

• RBCs lose their nucleus and most organelles as they mature, increasing space for hemoglobin.

• Mature RBCs are specialized for oxygen transport.

Blood Types: ABO and Rh Systems

• ABO System: Determined by the presence of A and B antigens on RBCs.

• Rh System: Determined by the presence (+) or absence (−) of the Rh antigen (D antigen).

Hemostasis (Blood Clotting) Steps

1. Vascular spasm (blood vessel constriction)

2. Platelet plug formation

3. Coagulation (formation of a fibrin clot)

Differences Between Arteries, Veins, and Capillaries

Vessel Type	Structure	Function
Arteries	Thick, muscular walls	Carry blood away from the heart
Veins	Thinner walls, valves present	Carry blood toward the heart
Capillaries	One cell thick	Exchange of gases, nutrients, and wastes

Fate of Old/Damaged RBCs

• Old RBCs are removed by the spleen and liver.

• Hemoglobin is broken down; iron is recycled, and bilirubin is excreted in bile.

Function of Hemoglobin

• Hemoglobin binds oxygen in the lungs and releases it in tissues.

• Also transports some carbon dioxide from tissues to lungs.

Main Blood Disorders

• Anemia: Deficiency in RBCs or hemoglobin, leading to reduced oxygen transport.

• Leukemia: Cancer of white blood cells.

• Jaundice: Yellowing of skin/eyes due to excess bilirubin.

• Platelet Deficiency: Leads to problems with blood clotting.

Heart and ECG

Heart Chambers, Valves, and Coronary Arteries

• Chambers: Right atrium, right ventricle, left atrium, left ventricle.

• Valves: Tricuspid, pulmonary, mitral (bicuspid), aortic.

• Coronary Arteries: Supply blood to the heart muscle itself.

SA Node and Pacemaker Function

• The SA node (sinoatrial node) is the heart's natural pacemaker, initiating electrical impulses that set the heart rate.

ECG Waves and Their Representation

• P wave: Atrial depolarization (contraction).

• QRS complex: Ventricular depolarization (contraction).

• T wave: Ventricular repolarization (relaxation).

Muscle Types in the Heart

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

• Skeletal Muscle: Voluntary, striated, attached to bones.

• Smooth Muscle: Involuntary, non-striated, found in vessel walls and organs.

Cardiac muscle contracts involuntarily and rhythmically, while skeletal muscle contraction is voluntary and smooth muscle contraction is involuntary and slow.

How Skeletal Muscles Help Return Blood to the Heart

• Skeletal muscle contractions compress veins, helping to push blood back toward the heart (muscle pump mechanism).