Human Tissue Study Quiz

Human Anatomy and Physiology 1 - Summary of Syllabus

• The syllabus covers the relationship between structure and physiology in mammals, including important bodily functions and processes.
• It includes the study of cells, tissues, and their relationship to function in mammals.
• The syllabus also covers the digestive, respiratory, cardiovascular, immune, and musculoskeletal systems.
• Malfunctions associated with these systems are also part of the study.

Tissues - Definition and Classification

• Tissues are collections of similar cells that perform a specific function in the structuring and operation of the body.
• Histology is the study of tissues.
• Tissue cells are bound together by a non-living intercellular matrix.
• The intercellular matrix is secreted by the cells themselves.
• The matrix composition varies between tissue types and can be liquid, semi-solid, or solid.
• Blood, for instance, has a liquid matrix, enabling its flow within vessels.
• Bone is an example of tissue with a solid matrix, providing structural support.

Tissue Classification

• Tissues are classified into four main groups:
  • Epithelial tissues: These tissues cover body surfaces, line body cavities and lumen cavities of organs, and form glands.
  • Muscular tissues: Responsible for movement in the body by contracting.
  • Connective tissues: These include blood, cartilage, bone, connective tissue proper, and associated products.
  • Nervous tissues: Initiates and transmits impulses between different parts of the body

Epithelial Tissues - Characteristics and Examples

• Epithelial tissues generally:
  • Consist mostly of cells with limited extracellular material between them.
  • Cover external and internal surfaces of the body, body cavities and vessels.
  • Form glands (eg. salivary glands)
  • Have a free surface not associated with other cells and a basal surface.
  • The basal surface attaches to a basement membrane.
  • Some epithelial tissues lack a free surface or a basement membrane. For example, endocrine gland cells do not have a free surface and do not rest on a basement membrane.
• Specialized cell contacts (tight junctions and desmosomes) bind adjacent cells.
• Blood vessels do not penetrate the basement membrane. Gases and nutrients diffuse from blood vessels in the underlying connective tissue to reach the epithelium.
• In epithelia with multiple layers of cells, the metabolically active cells are close to the basement membrane; those further away from the basement membrane die.
• Epithelia are avascular but usually innervated.
• They retain mitotic ability to regenerate damaged or worn-off cells.
• They are exposed to friction, and their surfaces wear off. They replenish themselves through mitosis.
• They are also susceptible to harm from hostile environmental substances.
• Classified based on the number of cell layers and the shape of the exposed surface cells.

Classification of Epithelium

• Epithelium is classified into two main types: membranous and glandular.

• Membranous epithelia line body surfaces, cavities, and lumina. They are specialized for protection and absorption. -One side of the membranous epithelium is exposed to a body surface, lumen, or the skin surface.

  • Some are derived from ectoderm (outer layer of skin), others from mesoderm (e.g., lining of blood vessels), and still others come from endoderm (e.g., inner lining of the gastrointestinal tract).

• Membranous epithelia are avascular and nourished by diffusion from underlying connective tissues. Cells are tightly packed with scant intercellular matrix between them.

• Different epithelial function.

• Cover or line surfaces for protection from pathogens, absorption of digested products, and filtration (e.g., in the kidney).

• Specialized structures like those in the air sacs of the lungs facilitate diffusion.

• Neuro-epithelial cells respond to chemical molecules and act as chemoreceptors in taste buds and the nasal regions.

• Types of membranous epithelium are classified by the number of layers of cells and the shape of cells on the exposed surface.

Simple Epithelium

• Simple epithelium is composed of flattened or irregularly shaped cells tightly bound together.
• Each cell contains an oval, centrally located nucleus.
• Cells range from thin, flattened cells to columnar depending on function.
• Cells may exhibit surface specializations like cilia and microvilli.
• Simple squamous epithelium: Flattened, scale-like, irregular cells with a central nucleus. Adapted for diffusion and filtration and absorption. Found in air sacs, parts of the kidney, and the lining of blood vessels (endothelium), and lining body cavities (mesothelium).
• Simple cuboidal epithelium: Composed of tightly fitted hexagonal cells (as tall as they are wide). Some have cilia and microvilli. Found in small ducts and tubules with excretory, secretory, or absorptive functions (e.g., ovaries, terminal bronchioles, smallest ducts of kidney tubules).
• Simple columnar epithelium: Composed of tall columnar cells, height varies depending on location/function. Some have cilia or microvilli. Found in areas involved in secretion or absorption (e.g., digestive tract, bronchioles).
• Simple ciliated columnar epithelium: Characterized by cilia on the free surface. Aids in transporting substances via wave-like movements. Found in uterine tubes.
• Pseudostratified ciliated columnar epithelium: Single layer of cells attached to the basement membrane, but some cells are tall and thin and reach the free surface of the epithelium. Appears stratified due to varying cell heights. Commonly found in respiratory epithelium; functions in mucus and fluid movement.

Stratified Epithelium

• These tissues consist of two or more layers of cells.
• They regenerate from below (the basal cells divide and push newly formed cells upward to replace older cells).
• They are more durable than simple epithelia.
• They are poorly suited for absorption & secretion due to their thickness, but perform protective functions.
• Classification is based on the shape of the surface layer of cells (which are in contact with the basement membrane.
• Stratified squamous epithelium: Composed of multiple layers of cells, with surface cells being squamous. Deeper layers can be columnar or cuboidal. Mitosis occurs only in the deepest layer. This type is categorized as keratinized or non-keratinized.
  • Keratinized: Forms the epidermis of the skin; provides protection against abrasion, desiccation, and bacterial invasion.
  • Non-keratinized: Forms the mucosa of the mouth, throat, and other areas; provides protection against abrasion but not fluid loss.
• Stratified cuboidal epithelium: Found in sweat glands, salivary or some larger ducts. • Stratified columnar epithelium: Found in some parts of the larynx, the male urethra. • Transitional epithelium: Unique stratified epithelium that lines urinary bladder and ureters. Highly adaptive to permit tissue distension (stretching). Basal cells appear columnar or cuboidal, but the surface cells flatten when stretched.

Body Membranes

• These are thin epithelial layers that cover, separate, and support visceral organs and line body cavities.
• Two basic types: mucous and serous membranes.
• Mucous membranes: Line body cavities and tubes that open to the exterior (e.g., nasal and oral cavities, respiratory, urinary, and digestive tracts). Secrete mucus, which lubricates and protects.
• Serous membranes: Line the thoracic and abdominal cavities and cover visceral organs. Secrete serous fluid, a watery lubricant, reducing friction.
  • Types of serous membranes:
    • Pleurae: Associated with the lungs.
    • Pericardium: Associated with the heart.
    • Peritoneum: Associated with the abdominal cavity. Visceral (adheres to the outer surface of organ) & Parietal (lines the cavity).

Glandular Epithelium

• Specialized tissues in the body with secretory functions.
• Glands are made of epithelium supported by connective tissue.
• Exocrine glands: Glands with ducts; ducts are lined with epithelium. These secrete their products into ducts that open onto a surface. Examples include sweat glands and salivary glands
• Endocrine glands: Glands without ducts. They secrete hormones into the bloodstream. Examples include thyroid glands and pituitary glands
• Classification of exocrine glands is based on the shape of their secretory units (alveoli or acini) and the branching pattern of their ducts (simple or compound).
• Unicellular glands: Consist of a single cell e.g. Goblet cells in the respiratory and digestive systems. These cells secrete mucus. • Multicellular glands: Composed of many cells. • Merocrine glands: Secrete products via exocytosis without loss of cellular material e.g. most salivary and sweat glands. • Apocrine glands: Secrete products with some cellular material pinched off; mammary glands. • Holocrine glands: Secrete products by rupturing entire cells, e.g., sebaceous glands

Connective Tissues

• Tissues comprised of cells separated by a non-living extracellular matrix.
• Exceptionally vascular, and with the exception of mature cartilage, well nourished.
• The extracellular matrix (ECM) is largely responsible for connective tissue function. Types of connective tissue cells ending in “-cytes” maintain, and “-clasts” break the matrix down. Fibroblasts provide fibrous components.
• Classifications include embryonic connective tissue (mesenchyme) and connective tissue proper. The matrix has three components: protein fibers (collagen, reticular, elastic), ground substance, and fluid.
  • Collagen fibers: Very strong and flexible but relatively inelastic.
  • Reticular fibers: Fine collagenous fibers forming a network.
  • Elastic fibers: Elastic protein that can return to its original shape after being stretched.
• Embryonic connective tissues: Mesenchyme: Undifferentiated cells in masses of homogenous jelly-like matrix; the origin of connective tissues.
• Connective tissue proper: Has 6 types, including:
  • Loose (Areolar) connective tissue: A binding and packing material that joins tissues and organs, supporting skin, and surrounding blood vessels. Contains mast cells that produce heparin (anticoagulant) and histamine (e.g. vasodilator).
  • Dense regular connective tissue: Composed primarily of collagenous fibers; forms tendons & ligaments (muscle-bone, bone-bone connections).
  • Dense irregular connective tissue: Densely packed collagen fibers; interwoven to provide tensile strength (in skin, joint capsules).
  • Elastic connective tissue: Predominantly elastic fibers; found in walls of large arteries, some lung tissues.
  • Reticular connective tissue: Network of reticular fibers. Supports parts like liver, spleen, lymph nodes.
  • Adipose tissue: Specialized connective tissue with fat cells (adipocytes) for energy storage, insulation & cushioning.
• Cartilage tissues: Supportive connective tissues found between bones at joints (e.g., hyaline, fibrocartilage, elastic cartilage), and providing support to structures like the trachea. They consist of chondrocytes within a firm, semi-solid matrix and lack significant blood vessels.
  • Hyaline cartilage: The most widespread type of cartilage; most common type in the body; covers bone surfaces in joints, found in the nose, trachea, and larynx.
  • Fibrocartilage: Contains a matrix densely strengthened with collagen fibers. Adapted to withstand tension & compression; found at the pubic symphysis and between vertebrae (e.g., intervertebral discs).
  • Elastic cartilage: Similar to hyaline cartilage except for the presence of elastic fibers, making it flexible, e.g., outer ear, epiglottis, parts of the larynx.
• Bone tissue (osseous connective tissue): The most rigid connective tissue. Contains a rich vascular supply and significant metabolic activity. Hardness is due to calcium phosphate deposits within the matrix, and collagen fibers give flexibility. - Compact bone: The hard outer layer. - Spongy (cancellous) bone: Porous, highly vascularized inner layer. - Osteocytes occupy cavities called lacunae.

Blood

• Blood is a fluid connective tissue; it plays a crucial role in maintaining internal homeostasis.
• It transports oxygen and carbon dioxide, hormones, nutrients, and waste products. Protects the body from infections and regulates temperature
• Plasma: Straw-colored fluid (mostly water); dissolved substances like ions, proteins, hormones, waste products, gases, & enzymes.
• 45% formed elements,
  • Erythrocytes (Red Blood Cells): Flattened, biconcave disks; transport oxygen via hemoglobin. Contain a nucleus at maturation. Life Span ~ 120 days; recycled in spleen & liver.
  • Leukocytes (White Blood Cells): Amoeboid shape; involved in defense against pathogens. Divided into granular (neutrophils, eosinophils, basophils) and agranular (lymphocytes, monocytes) types.
  • Platelets (Thrombocytes): Cell fragments involved in blood clotting. Lacks a nucleus, small in size.

Muscular Tissues

• Muscle tissues are primarily responsible for movement in the body.
• Cells are elongated in the direction of movement; grouped according to structure (with or without striations) and functional mechanism (voluntary or involuntary)
• Skeletal muscle: Striated, voluntary muscle attached to bones, facilitates voluntary movements. Elongated multinucleated fibers with transverse striations.
• Smooth muscle: Non-striated, involuntary muscle found in walls of internal organs (e.g., digestive tract, blood vessels): Enables involuntary movements. Spindle-shaped cells with a single centralized nucleus.
• Cardiac muscle: Striated, involuntary muscle found only in the heart. Cylindrical, branching cells with a single, centralized nucleus; electrically connected through intercalated discs; enables rhythmic contractions for pumping blood.

Nervous Tissue

• Composed of neurons (initiate, transmit impulses), and neuroglia (support, bind neurons). Neurons consist of a cell body (contains the nucleus), dendrites (receive stimuli), and axon (transmits impulses).
• Neuroglia supports neurons, providing nutrition, protection against infectious agents, & insulation.
• Nervous tissue is found in the brain, spinal cord, and nerves. Characterized by having electrical signals that transmit impulses. Neuroglia is also high in abundance, as many neuroglia types to every one type of cell.

Digestive System

• The digestive system prepares food for cellular utilization via four main processes: • Motility: Movement of food through the digestive tract (e.g., ingestion, mastication, swallowing, peristalsis) • Secretion: Both exocrine (secrete into ducts: water, HCl, HCO3-, many enzymes into the GIT e.g., stomach secretions include 2-3 litres of gastric juice daily) and endocrine (secretions into blood; hormones produced by stomach and intestines help regulate digestive system) secretions. • Digestion: Breakdown of complex food molecules (into absorbable units). • Absorption: Passage of digested food molecules into blood or lymph.
• The system is composed of a tubular GIT (alimentary canal -oral cavity, pharynx, esophagus, stomach, small intestine, large intestine) and accessory digestive organs (teeth, tongue, salivary glands, liver, gallbladder, pancreas).

Layers of the GIT

• The GIT from the stomach to the anal canal has four layers (tunics) • Mucosa: Absorbs and secretes. Contains simple columnar epithelium, goblet cells (secrete mucus), and lamina propria (connective tissue with lymph nodules). Below lamina propria is smooth muscle (muscularis mucosae). • Submucosa: Thick, highly vascular connective tissue; absorbs digested molecules and contains glands and nerve plexuses (Meissner's plexus). • Muscularis: Two layers of smooth muscle (inner circular layer, outer longitudinal layer). Responsible for segmental contractions and peristaltic movement. Myenteric (Auerbach's) plexus innervates muscularis. • Serosa/Adventitia: Outermost layer that provides protection and binding; consists of loose connective tissue covered by simple squamous epithelium, and is the visceral peritoneum of the abdominal cavity. (Contains sympathetic & parasympathetic fibers from the ANS.)

Mouth, Pharynx, and Associated Structures

• Mouth: Cheeks, lips, hard and soft palate, tongue. Mechanical digestion of food (mastication) begins, initiates bolus formation. Lined with non-keratinized
• Pharynx Common passageway for respiratory and digestive systems; has three regions: nasopharynx (respiratory), oropharynx (digestive + respiratory), laryngopharynx (digestive). Composed of skeletal muscle and mucosa; has tonsils.
• Tongue: Aids in mastication and swallowing. Contains taste buds for taste sensation (Filiform, Fungiform, Vallate papillae). Has extrinsic (genioglossus, styloglossus, hyoglossus) and intrinsic muscles.

Salivary Glands

• Accessory organs that produce saliva; helps with food digestion & taste.
• Three pairs are parotid, submandibular, sublingual; all located outside the oral cavity. Function is to produce saliva, which cleanses the teeth & dissolves food molecules for taste.
• Saliva has enzymes and mucous cells.
• Innervation & stimulated secretion (sympathetic, parasympathetic).

Respiration

• Respiration involves: ventilation (breathing), gas exchange (air ↔ blood & blood ↔ tissue), oxygen utilization by the tissues (respiration).
• The respiratory system has organs like the nose (with nasal cavity - external portion is visible from the face & internal nasal cavity is the pathway for air; warms & filters the air), Pharynx (nasal/oral/laryngeal portions), Larynx (voice box), Trachea (windpipe), Bronchial Tree/bronchioles (branches), & Lungs. The lungs are associated organs, & gas exchange occurs in the alveoli.
• Breathing has inhalation & exhalation phases. Inhalation: Thoracic cavity volume increases by muscle contractions (Diaphragm contracts), creating a lower pressure relative to atmospheric pressure → Air rushes in.
• Exhalation: Thoracic cavity volume decreases (internal intercostal & abdominal muscles contract), creating higher pressure relative to atmospheric pressure → Air is forced out.

Musculoskeletal System

• The skeletal and muscular system interact and work together to enable movement.
• Skeletal muscles: Groups of muscles involved in movement of limbs; they work in pairs- contracting one muscle causes the other to relax- & attach on each end to bones..
• Skeletal muscles components:
  • Tendons (tough connective tissue) joining muscle-bone connections.
  • Insertion (bone end undergoing movement), Origin (stationary end)..
• Major muscle groups:
  • Head and neck: Ocular muscles (6 extrinsic ocular muscles -superior, inferior, lateral, medial rectus muscles, & superior, inferior oblique muscles), Mastication muscles (temporalis, masseter, pterygoid), Neck muscles (sternocleidomastoid, trapezius, splenius capitus)
• Thorax: Intercostal muscles for breathing (external, internal), diaphragm (major movement in quiet breathing)
• Appendicular Skeleton: Pectoral Girdle (trapezius, levator scapulae, rhomboideus, serratus anterior, pectoralis minor, subclavius), Arm (deltoid, supraspinatus, infraspinatus, teres major, teres minor), Forearm (flexor carpi radialis, palmaris longus, flexor carpi ulnaris, superficial/deep digital flexor, flexor pollicis longus), Lower Limb (thigh, hamstring groups-semitendinosus, biceps femoris, semimembranosus, gluteus maximus, medius, minimus, tensor fasciae latae), Leg (gastrocnemius, soleus, peroneus), Foot (intrinsic foot muscles)..

Immune System

• A complex network of mechanisms & anatomical components protecting the body from pathogens.

• Non-specific/innate mechanisms:

• Physical barriers (skin, mucous membranes) protect the body.

• Chemical barriers (e.g., gastric acid kill pathogens).

• Phagocytes (neutrophils, monocytes/macrophages) engulf and destroy pathogens.

• Specific/adaptive mechanisms:

• Lymphocytes (T & B lymphocytes) target specific pathogens & act in response to infection.

• Antibodies (immunoglobulins IgG, IgA, IgM, IgD, IgE) bind to specific pathogens to disable or eliminate them.

• The ability to mount a specific immune response (immunological competence) develops only after about one month of birth. The fetus does not immunologically reject the mother. Immunization programs are used for vaccination which stimulate active immunity that offers protection against future infections for some diseases. Passive immunity involves transfers antibodies - mother to fetus, & or another person e.g. after immunizations.