lecture 4

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Questions and Answers

Which type of muscle tissue is under involuntary control and found in the heart?

Epithelial tissue

Smooth muscle

Skeletal muscle

Cardiac muscle (correct)

Skeletal muscle tissue is responsible for involuntary movement.

False

What are the two main types of cells found in nervous tissue?

neurons and neuroglia

Smooth muscle tissue facilitates __________ of airways.

constriction Signup and view all the answers

Match the tissue type with its primary function:

Skeletal muscle = Voluntary movement and heat generation Cardiac muscle = Forms the heart wall Smooth muscle = Involuntary control of internal organs Nervous tissue = Coordinates and controls body responses Signup and view all the answers

Which of the following types of tissues is responsible for generating body heat?

Muscular tissue Signup and view all the answers

Epithelial tissue is specialized for exchange with only the internal environment of the body.

False Signup and view all the answers

What is the scientific study of tissues called?

Histology Signup and view all the answers

The primary connective function of connective tissue is to protect and __________ the body and internal organs.

support Signup and view all the answers

What type of junction forms leakproof connections?

Tight junctions Signup and view all the answers

Desmosomes connect adjacent cells and resist __________.

contraction Signup and view all the answers

Match the following types of tissues with their functions:

Epithelial tissue = Covers and protects the body Connective tissue = Connects organs and stores energy Muscular tissue = Generates force and body heat Nervous tissue = Detects stimuli and generates nerve impulses Signup and view all the answers

What type of cell junction anchors cells to the underlying basement membrane?

Hemidesmosomes Signup and view all the answers

What process do merocrine glands use to release their products?

Exocytosis Signup and view all the answers

Apocrine glands secrete products from the entire surface of the cells.

False Signup and view all the answers

What type of connective tissue contains mesenchymal cells?

Mesenchymal tissue Signup and view all the answers

Sebaceous glands are an example of ________ glands.

holocrine Signup and view all the answers

Match the following types of connective tissue with their descriptions:

Loose connective tissue = Contains a variety of cells and fibres, serves as packing material Dense connective tissue = Packed with protein fibres, fewer cells Adipose connective tissue = Stores energy and insulates the body Reticular connective tissue = Filters substances like lymph Signup and view all the answers

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

Stratified squamous epithelium Signup and view all the answers

Collagen fibers are the thinnest type of fibers in the extracellular matrix.

False Signup and view all the answers

Name the process by which cells in holocrine glands release their secretions.

Rupturing Signup and view all the answers

The main component of the extracellular matrix is _________.

ground substance Signup and view all the answers

Which type of fiber in the extracellular matrix provides elasticity?

Elastic fibers Signup and view all the answers

Epithelial tissues typically have a larger number of cells compared to connective tissues.

True Signup and view all the answers

What is the primary function of macrophages in connective tissue?

Phagocytosis Signup and view all the answers

The densely packed connective tissue that is irregularly arranged is known as ________ connective tissue.

dense Signup and view all the answers

Which of the following glands is correctly paired with its secretion method?

Holocrine - secrete by cell rupture Signup and view all the answers

What types of layers can epithelial tissue have?

Simple and stratified Signup and view all the answers

The primary function of the basement membrane is to allow nutrient absorption.

False Signup and view all the answers

What are the primary functions of epithelial tissues?

Protection, secretion, absorption. Signup and view all the answers

The _____ membrane connects epithelial tissue to underlying connective tissue.

basement Signup and view all the answers

Which type of epithelium is specialized for filtration and diffusion?

Simple squamous epithelium Signup and view all the answers

Cilia in epithelial tissue assist in the secretion of mucus.

True Signup and view all the answers

Name a gland type that secretes hormones directly into the bloodstream.

Endocrine glands Signup and view all the answers

The ciliated pseudostratified columnar epithelium lines the majority of the _____ tract.

upper respiratory Signup and view all the answers

Which type of epithelial tissue is characterized by multiple layers of flat cells?

Stratified squamous epithelium Signup and view all the answers

Goblet cells are found in ciliated simple columnar epithelium.

True Signup and view all the answers

What is the shape of cells in cuboidal epithelium?

Cube-shaped Signup and view all the answers

Stratified cuboidal epithelium is _____, meaning it is not commonly found in many areas of the body.

rare Signup and view all the answers

Match the epithelial types to their functions:

Simple squamous = Filtration and diffusion Ciliated columnar = Movement of mucus Stratified squamous = Protection from abrasion Transitional = Expansion of hollow organs Signup and view all the answers

The basal surface of epithelial cells faces the external environment.

False Signup and view all the answers

What characteristic describes epithelial cells as 'polarized'?

They have distinct apical and basal surfaces. Signup and view all the answers

Which type of dense connective tissue is characterized by packed collagen fibers and provides great tensile strength?

Dense regular connective tissue Signup and view all the answers

Elastic connective tissue provides rigidity and structure to organs.

False Signup and view all the answers

What structure do chondrocytes reside in within cartilage?

lacunae Signup and view all the answers

Hyaline cartilage provides a smooth surface between bones at _________.

joints Signup and view all the answers

Match the following types of cartilage with their characteristics:

Hyaline = Most abundant cartilage, provides smooth surfaces at joints Fibrocartilage = Strongest type of cartilage, found in intervertebral discs Elastic = Provides strength and stretch, shapes structures like the ear Signup and view all the answers

Which of the following is a function of blood?

Transports oxygen, nutrients, gases, and wastes Signup and view all the answers

Mucous membranes line cavities that are not open to the external environment.

False Signup and view all the answers

What are the cells that secrete synovial fluid in synovial membranes called?

synoviocytes Signup and view all the answers

The primary component of blood plasma is _________.

water Signup and view all the answers

Which type of connective tissue is characterized as 'uncooked egg' in appearance?

Synovial membranes Signup and view all the answers

The epidermis is the deepest layer of the skin.

False Signup and view all the answers

What type of connective tissue forms the framework for organs and supports various body structures?

areolar connective tissue Signup and view all the answers

Fibrocartilage is found at the pubic _________.

symphysis Signup and view all the answers

Match the following membranes with their functions:

Mucous membranes = Line body cavities open to the external environment Serous membranes = Lubricate and protect organs not exposed to the external environment Cutaneous membranes = Protect against abrasion and environmental damage Signup and view all the answers

Which cells are primarily responsible for detecting electrical stimuli and producing action potentials?

Excitable cells Signup and view all the answers

Study Notes

Tissues

Tissues are groups of similar cells working together to perform a shared function.
Histology is the study of tissues.
Four types of human tissue:
- Epithelial tissue
- Connective tissue
- Muscular tissue
- Nervous tissue

Epithelial Tissue

General Functions:
- Covers and protects the body
- Lines hollow organs
- Forms glands
- Facilitates exchange with the environment

Connective Tissue

General Functions:
- Protects and supports the body and internal organs
- Connects organs together
- Stores energy
- Aids immunity

Muscular Tissue

General Functions:
- Generates force through contraction
- Produces body heat

Nervous Tissue

General Functions:
- Detects and responds to stimuli.
- Generates electrical signals (nerve impulses) to control muscle and gland activity.

Cell Junction Types

Cell junctions act as points of contact between adjacent cells.
Five main types:
- Tight junctions
- Adherens junctions
- Desmosomes
- Hemidesmosomes
- Gap junctions

Tight Junctions

Function: Form leakproof connections between cells
Location: Stomach lining, intestinal epithelium, urinary bladder

Adherens Junctions

Function: Connect adjacent cells, resist pulling forces.
Structure:
- Transmembrane proteins
- Cytoplasmic plaque
- Microfilaments (actin)

Desmosomes

Function: Connect adjacent cells, resist contraction.
Structure:
- Similar to adherens junctions
- Plaque connects transmembrane proteins to intermediate filaments.
Location: Epidermis, heart muscle

Hemidesmosomes

Function: Anchor cells to underlying tissues.
Structure:
- Transmembrane glycoproteins connect intermediate filaments to laminins in the basement membrane.
Location: Epidermis, anchoring skin to connective tissue

The Basement Membrane

Structure: Two layers:
- Basal lamina
- Reticular lamina
Function:
- Separates epithelial tissue from underlying connective tissue.
- Provides a surface for epithelial attachment, migration, and growth.

Gap Junctions

Function: Allow direct cell-to-cell communication through protein channels (connexons) formed by connexins.
Location: Nerves (electrical synapses), allowing ion flow.

Epithelial Tissue Classification

Classified based on:
- Number of layers:
  - Simple (one layer)
  - Stratified (multiple layers)
  - Pseudostratified (single layer appearing as multiple layers)
- Shape of cells:
  - Squamous (flat)
  - Cuboidal (cube-shaped)
  - Columnar (long and rectangular).
  - Transitional (variable shape)

Epithelial Cell Polarization

Polarized cells: Cells with distinct "faces" or ends.
Apical surface: Faces inward (organ, vessel, duct) or outward (external environment)
Basal surface: Faces underlying tissues (usually connective tissue)
Lateral surface: Faces adjacent cells.

Surface Epithelium

Lines body surfaces.

Simple Squamous Epithelium

Function:
- Filtration of body fluids
- Diffusion of nutrients and gases
Location:
- Endothelium (lining blood vessels)
- Mesothelium (epithelial layer of serous membranes)

Simple Cuboidal Epithelium

Function:
- Secretion of hormones and other substances.
- Absorption of water and solutes
Location:
- Kidney tubules
- Thyroid gland

Non-ciliated Simple Columnar Epithelium

Function:
- Secretion of mucus
- Absorption of nutrients.
Structure:
- Contains goblet cells and gastrointestinal cells with microvilli
Location:
- Digestive tract lining

Ciliated Simple Columnar Epithelium

Function: Cilia on apical surface move mucus produced by goblet cells
Location:
- Bronchioles
- Oviducts

Non-ciliated Pseudostratified Columnar Epithelium

Function: Absorption and secretion (e.g., saliva)
Structure: Single layer appears stratified due to nuclei at different depths.
Location:
- Epididymis
- Part of the male urethra

Ciliated Pseudostratified Columnar Epithelium

Function: Cilia sweep mucus over the tissue surface.
Location:
- Majority of the upper respiratory tract

Stratified Squamous Epithelium (Keratinized)

Function: Protection from abrasion, fluid loss, UV radiation, and invasion.
Structure: Superficial layer can be sloughed off, and contains keratin (filamentous, insoluble protein for strength).
Location:
- Epidermis (skin)

Stratified Squamous Epithelium (Nonkeratinized)

Location:
- Lining of the vagina

Stratified Cuboidal Epithelium

Function: Protection from abrasion.
Location:
- Sweat glands
- Esophageal glands
- Parts of the male urethra

Stratified Columnar Epithelium

** Function:**
- Protection from invasion
- Secretion (e.g., tears).
Location:
- Esophageal glands
- Conjunctiva

Transitional Epithelium (Urothelium)

Function: Lines hollow organs that expand to store fluids.
Structure:
- Cuboidal at rest.
- Squamous when stretched.
Location:
- Urinary bladder
- Portions of the ureters and urethra

Glandular Epithelium

Function: Secretion for body protection.
Types:
- Exocrine
- Endocrine
- Mixed

Exocrine Glands

Function: Secrete substances a short distance.
Secretion pathway:
- Into ducts that carry secretions to the surface of the body or into hollow organs.

Endocrine Glands

Function: Secrete hormones into the interstitial fluid, which diffuses into the blood and circulates to target tissues.
Hormones: Chemical messengers produced by cells that regulate homeostasis.
Example: Thyroxin (thyroid hormone)

Multicellular Exocrine Glands

Types:
- Merocrine
- Apocrine
- Holocrine

Merocrine Glands

Secretion method: Exocytosis
Example: Most body glands, including sweat glands.

Apocrine Glands

** Secretion method:** Exocytosis only from the apical surface.
Example: Mammary glands (secreting breast milk)

Holocrine Glands

Secretion method: Cell rupture, releasing contents into the secretion.
Example: Sebaceous glands (secrete oil)

Connective Tissues

General Characteristics:
- Not usually found at body surfaces.
- Contains nerves and blood vessels (with some exceptions).
Components:
- Extracellular matrix (ECM)
- Cells

Extracellular Matrix (ECM)

Structure:
- Protein fibers (collagen, elastic, reticular)
- Ground substance
Properties: Can be liquid, solid, or gel-like.

Connective Tissue Cells

** Originate from embryonic mesenchymal cells.**
Types:
- Fibroblasts (most abundant, secrete ECM of loose and dense connective tissue)
- Macrophages (phagocytic immune cells)
- Plasma cells (secrete antibodies)
- Mast cells (release inflammatory chemicals)
- Adipocytes (store triglycerides)
- Leukocytes (white blood cells)

ECM of Connective Tissues

Ground substance: Material between cells and fibers, giving the tissue its properties.
Protein fibers:
- Collagen fibers (most abundant, provide tensile strength)
- Elastic fibers (provide elasticity)
- Reticular fibers (thin, provide support)

Difference between Epithelial and Connective Tissue

Key difference: Ratio of extracellular matrix to number of cells.
- Epithelial tissues have more cells.
- Connective tissues have more extracellular matrix.

Other Differences between Epithelial and Connective Tissue

Vascularization: Epithelial tissue is typically not vascularized (lacks blood vessels), while connective tissue is vascularized.
Location: Epithelial tissues often form the most superficial layer and are not covered by other tissues.

Embryonic Connective Tissues

Mesenchymal tissue:
- Contains mesenchymal cells, semifluid ground substance, and reticular fibers.
- Develops into nearly all types of connective tissue.
- Forms the first skeleton of the developing embryo.
Mucoid connective tissue:
- Contains fibroblasts, gel-like ground substance, and thin collagen fibers.
- Provides mechanical support to overlying tissue.
- Found in the umbilical cord.

Mature Connective Tissues

Loose connective tissue:
- Sparsely distributed cells and fibers.
- Types: Areolar, adipose, and reticular connective tissue.
Dense connective tissue:
- Densely packed protein fibers, fewer cells than loose connective tissue.
- Types:
  - Regular
  - Irregular
  - Elastic.

Areolar Connective Tissue

Function: Supports, reinforces, provides stretch to organs, serves as packing material for body cavities.
Structure:
- All three fiber types (collagen, elastic, reticular)
- Variety of cells
- Semifluid ground substance.

Adipose Connective Tissue

Function: Insulates the body, stores energy, supports and protects internal organs.
Structure:
- Contains adipocytes (store triglycerides).
- Two types:
  - White adipose tissue (stores triglycerides in a large central droplet)
  - Brown adipose tissue (contains numerous mitochondria, involved in heat production).

Reticular Connective Tissue

Function: Filters substances, forms stroma of the spleen and lymph nodes.
Structure:
- Tightly woven reticular fibers
- Fibroblasts

Dense Regular Connective Tissue

Function: Provides great tensile strength.
Structure:
- Packed collagen fibers
- Sparse fibroblasts.
Location: Tendons, ligaments, aponeuroses.

Dense Irregular Connective Tissue

Function: Resists pulling forces along any axis.
Structure:
- Irregularly arranged collagen fibers
- Few fibroblasts.
Location: Fasciae, pericardium.

Elastic Connective Tissue

Function: Provides elasticity to organs.
Structure:
- Elastic fibers
- Few fibroblasts.
Location:
- Lungs
- Walls of elastic arteries
- Trachea
- Bronchial tubes.

Supporting Connective Tissues: Cartilage

Function:
- Provides smooth surfaces between bones (hyaline cartilage)
- Resists compression (all types of cartilage)
Structure:
- Thick collagen fibers in a gel-like ground substance.
Cells: Chondrocytes (fibroblasts) reside in lacunae.
Vascularization: Not vascularized, heals slowly.
Perichondrium: Layer of new chondrocytes containing blood vessels that covers some types of cartilage.

Types of Cartilage

Hyaline cartilage:
- Most abundant type, forms the fetal skeleton before ossification.
- Found at joints.
Fibrocartilage:
- Strongest type, lacks a perichondrium.
- Found at the pubic symphysis, intervertebral discs, and menisci (knee joints).
Elastic cartilage:
- Provides strength and stretch.
- Found in the auricle, eustachian tubes, and epiglottis.

Bone Tissue

Types: Compact and spongy.
Compact bone:
- Consists of repeating osteons, which are rings of calcified ECM with:
  - Lacunae containing osteocytes (bone cells)
  - Central canal (contains blood vessels and nerves)

Liquid Connective Tissues

Blood:
- Liquid ECM (blood plasma) containing blood cells, transporting oxygen, nutrients, gases, wastes, immune cells, hormones, and platelets.
Lymph:
- Liquid tissue with varying composition depending on location.
- Less protein than blood plasma.
- Composition:
  - Lymphocytes (exiting lymph nodes)
  - Dietary fats (exiting the small intestine)

Anatomical Membranes

Types:
- Mucous membranes
- Serous membranes
- Cutaneous membranes (skin).
Structure: Usually contain an epithelial layer and connective tissue, except for synovial membranes.

Mucous Membranes

Function:
- Line body cavities open to the external environment.
- Protect the body from invaders and fluid loss.
- Secrete enzymes for digestion and absorption.
Structure:
- Variable epithelial layer
- Connective tissue (lamina propria)

Serous Membranes

Function:
- Line internal body cavities and organs not exposed to the external environment.
- Lubricate organs and walls.
Structure:
- Areolar connective tissue covered by mesothelium (secretes serous fluid).

Cutaneous Membranes (Skin)

Function: Protection from abrasion, UV radiation, and invasion
Structure:
- Epidermis (keratinized stratified squamous epithelium)
- Dermis (dense irregular and areolar connective tissue)

Synovial Membranes

Function: Line and lubricate joints, nourish cartilage.
Structure:
- Contains only connective tissue.
- Synviocytes (secrete synovial fluid)
- Layers of areolar and adipose connective tissue.

Muscular and Nervous Tissues

Excitable cells: Detect electrical stimuli and respond by producing action potentials.

Muscular Tissue

Function:
- Contraction to move bones
- Generates heat
Structure:
- Made of muscle fibers (myocytes).
Types:
- Skeletal
- Cardiac
- Smooth

Nervous Tissue

Function:
- Detects and responds to stimuli.
- Generates nerve impulses.
Primary cell type: Neuron.
Supporting cells: Neuroglia.### Skeletal Muscle Tissue
Long, multinucleate, striated tissue
Responsible for voluntary movement, maintaining posture, and generating heat
Attaches to bones via tendons

Cardiac Muscle Tissue

Branched, striated fibres with a single nucleus
Cells joined by gap junctions for rapid electrical signal conduction
Under involuntary control
Collectively forms the myocardium or heart wall

Smooth Muscle Tissue

Long, nonstriated fibres in an irregularly-shaped cell with a single nucleus
Cells joined by gap junctions to coordinate involuntary muscle contractions
Facilitates peristalsis, constriction of airways, contractions of the urinary bladder and gallbladder

Nervous Tissue

Comprised of two types of cells: neurons and neuroglia
Neurons consist of a cell body, dendrites, and an axon and generate electrical signals
Neuroglia do not generate electrical impulses but synthesize myelin, a coating of neuronal axons, to increase electrical signal transmission speed

Summary of Tissue Types

Tissues are composed of cells and extracellular matrix (ECM)
Epithelial tissues cover and line the body, able to secrete/absorb substances and protect from mechanical injury
Connective tissues join epithelial tissues to deeper tissues and support the body
Muscular tissue moves the body and generates heat
Nervous tissue coordinates and controls the body's response to stimuli

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