Histology Y1 Flashcards
What is epithelium?
The tissue which covers and lines other tissues
- It is an avascular tissue
How is epithelium classified?
Number of layers (simple or stratified), she of the cell (squamous, cuboidal, columnar) and surface specialisation (keratinising)
What is the Basal lamina/Basement membrane?
The barrier between epithelium and underlying connective tissue
Pseudo stratified epithelium? Where is it found?
Falsely stratified - Nuclei are unevenly distributed and squished together - Usually in trachea and bronchus
Transitional epithelium? Where is it?
- When the bladder is empty and the cells are able to expand, when it is full they are squashed together
- Found in ureter and urinary bladder
Endocrine and exocrine glands
Endocrine - Secrets products directly into blood stream
Exocrine - Secrets products onto the skin via ducts
Exocrine gland types
Mucous gland - Secretes fluid used to lubricate and protect shown as brighter staining
Serous gland - Secretes Watery fluid, rich in enzymes that helps breakdown food shown as darker staining
Seromucous - mix of both
Either simple of compound depending if there’s a single or numerous branches
Can be acinar (more rounded) or tubular
Functions of connective tissue
- binding, support, protection, insulation, transportation and repair/scar tissue
CT is made of 3 main components
Cells, fibres and ground substances
Fibroblast function
- Found in CT
- Fixed cell
- ECM/collagen production allowing for structural support
Adipocyte function
- Found in CT
- Fixed cell
- Stores fat/energy and insulates
Macrophage function
- Found in CT
- Wandering cell
- Conducts phagocytosis
Plasma cell function
- Found in CT
- Wandering cell
- Produces antibodies
Mast cell function
- Found in CT
- Wandering cell
- Release inflammatory cytokines
White blood cell/Leukocytes
- Found in CT
- Wandering cell
- Defensive cell
Ordinary CT
Loose - Immediately below epithelium, surround capillaries (myelin)
Dense irregular - Found in dermis, collagen fibres are densely packed
Dense regular - Collagen fibres, found in ligaments and tendons
Specialised CT
Supportive - Cartilage (hayline, fibrocartilage or elastic)
Bone - Compact or spongy
Fluid - Blood or lymph
Adipose - Fat tissue
Collagen fibres (CT)
- High tensile strength
- Fibrils join to form fibres which join to form bundles
- Stretch resistant
Reticular fibres (CT)
- Brings larger collagen fibres together
- Individual fibres that don’t form bundles
- Branched, thin, collagenous fibres
Elastic fibres (CT)
- Long thin fibres that allow for stretch
- Found in the dermis, elastic arteries and lungs
Ground substances and what is in it?
- Gel where fibres and structures sit
- Composed of:
GAG’s, proteoglycans and adhesive glycoproteins
Functions of cartilage (CT)
Forms of supportive connective tissue
Where is Hyaline cartilage found (CT)
Joints, trachea, bronchus, costal cartilage (ribs), nasal cavities
Where is elastic cartilage found? (CT)
External ear, epiglottis (flap pf tissue beneath the tongue and back of the throat)
Where is fibrocartilage found?
Tendon insertions, intervertebral discs, pubic symphysis (joint) and articular meniscus
Functions of bone
- Main constituent of the skeleton, facilitates movement, supports and protects organs, harbours bone marrow (RBC production)
Types of bone
Spongy - Areas with numerous interconnecting cavities
Compact - Dense area without cavities (collagen fibres)
Osteoblasts
- Form bone ECM and are located at the surface of the bone
- Lay down bone
Osteocytes
- Maintains bone tissue
- Osteoblasts that have become trapped in bone matrix
- Located in the lacunae cavity
Osteoclasts
- Eats bone
- Large multi nucleated cells
- Forming a rough border of cells on the surface
Periosteum
newly lade bone
Types of muscle
Skeletal, cardiac, smooth
Identifying skeletal muscle
- striated lines of myosin and actin, long unbranched and multinucleate, nuclei preset on the periphery of fibres, found attached to bone
CT of skeletal muscle
Epimysium - Outside entire muscle
Perimysium - Surrounds each fascicle
Endomysium - Between each fibre
Sarcoplasm and sarcolemma
Sarcoplasm - Cytoplasm of fibre containing myofibrils, mitochondria, SER and myoglobin
Sarcolemma - Plasma membrane of fibres where calcium is stored and released
Identifying cardiac muscle/myocardium
- Striated dark and light bands, central nucleus position, branched cells joined together by intercalated
disk (junctions), has longitudinal and transverse sections
Identifying smooth muscle
- Found in tubule organs - Gut, blood vessels, bile duct, uterus, urinary bladder and respiratory tract
- Non striated, central nuclei with granules at poles
- Actin and myosin present but no banding
Nerve structure
- Composed of a cell body, soma containing a nucleus and an axon
Axons
- Transmission lines of the nervous system (bundles make up the nerve)
- Axons surrounded by endoneurium, fascicles surrounded by perineurium, nerve cell surrounded by epineurium
Types of nerve cells
Anaxonic - Axons cannot be distinguished from dendrites
Bipolar - Two sections separated by the cell body
Pseudounipolar - Single long axon with the soma on one side
Multipolar - Single axons and multiple dendrites so multiple sections
Dendrties
Receive stimuli from other cells and connect to the stoma
Schwann cells
Main supporting cell in PNS - Encloses each axon in myelin
- Can only myelinate 1 axon in PNS
Satellite cells
Located in PNS helping to support soma
Oligodendrocyte
Forms myelinated sheet for serval axons in CNS and can wrap around nerve multiple times which helps facilitate nerve impulse (CNS)
Astrocytes
Most common cell in CNS - Can be fibrous that are located in white matter or protoplasmic located in grey matter
Ependymal cells
Lines cavities of CNS such as the brain
Layers of the skin
- Epidermis
- Dermis
Hypodermis
Epidermis
- Top layer composed of stratified squamous keratinising epithelium
- Squamous cells are dead and filled with keratin proteins so it is a waterproof layer
Separated into 5 layers
Epidermis layers (Bottom to top)
Stratum basale - Cells divided mitotically
Stratum spinosum - Keratin fibres and lamellar bodies accumulate
Stratum granulosum - Keratohyalin granules and hard protein envelope form, lamellar bodies release lips and cells die
Stratum lucindum - Dead cells containing dispersed keratohylin
Stratum corneum - Dead cells with hard protein envelope, cells contain keratin and are surrounded boy lipids
Dermis
Made up off dense irregular connective tissue
Abundant in collagen with elastic and reticular fibres
Spilt into:
papillary (superficial) - Interdigitates with epidermal ridges of the epidermis
Reticular (deeper) - Attached to underlying hypodermis
- Thickness of skin relates to thickness of the dermis
Hypodermis
- Composed of CT and fat (not part of the true skin)
- Target for injection due to vascularity and so can absorb drug quickly
