General Histology (All)

Nephron

• Functional unit of the kidney

• Forms urine

T12-L3

The kidneys are located lateral to which vertebrae?

Renal fascia

Connective tissue layer that attaches to abdominal wall

Adipose capsule

Fat cushioning kidneyR

Renal capsule

• Fibrous sac

• Protects kidney from trauma and infection

Cortex

Composed of roughly 1.25 million nephrons

Renal papilla

Point of pyramid

Renal sinus

• Surrounded by renal parenchyma

• Contains blood & lymph vessels, nerves, urine-collecting structures

Blood vessels, renal corpuscle, renal tubule

3 main parts of nephrons

Glomerulus

• Fenestrated capillaries

• Initiates urine production

• Filtrate lacks cells & proteins

• Receives blood supply from afferent arteriole; drained by efferent arteriole

Renal corpuscle

The beginning of the nephron

• the nephron’s initial filtering component

Renal corpuscle

Composed of glomerulus and Bowman’s capsule

Efferent arterioles

Which arteriole’s diameter is smaller? (Efferent/Afferent)

Bowman’s capsule

• aka glomerular capsule

• Surrounds the glomerulus

• Composed of a visceral inner layer formed by podocytes

• Parietal outer layer composed of simple squamous epithelium

Visceral layer of podocytes

Fluids from blood in the glomerulus are filtered through the _____, resulting in the glomerular filtrate

Renal tubule

• Leads from glomerular capsule

• Ends at tip of medullary pyramid

• ~3cm long

• 4 major regions:

  • Proximal convoluted tubule

  • Nephron loop

  • Distal convoluted tubule

  • Collecting duct

Proximal convoluted tubule (PCT)

• Arises from glomerular capsule

• Longest, most coiled region

• Lies in cortex

• Lined by simple cuboidal epithelium with brush borders

• Prominent microvilli

Loop of Henle/Nephron Loop

• “U”-shaped, distal to PCT

• lies in medulla

• has ascending and descending limbs

Simple squamous epithelium

Lining of lower end of ascending limb of loop of Henle

Simple cuboidal epithelium

Lining of the distal portion of ascending limb of loop of Henle

Thick

(Thick/Thin) segment

• active transport of salts

• high metabolism, many mitochondria

Thin

(Thick/Thin) segments

• permeable to water

• low metabolism

Distal convoluted tubule (DCT)

• coiled, distal to nephron loop

• shorter and less coiled than PCT

• very few microvilli

• contacts afferent and efferent arterioles

• contact with peritubular capillaries

Collecting duct

• where DCTs of several nephrons empty into

• passes into medulla

• several merge into papillary duct (~30 per papilla)

• drain into minor calyx

Ureters

• pair of muscular tubules

• extend from renal pelvis to bladder

• oblique entry into bladder prevents backflow of urine

Transitional epithelium

Epithelium of ureter (mucosa)

Urinary bladder

• collapsible muscular sac

• stores and expels urine

Detrusor muscle

Muscle of urinary bladder

Internal urethral sphincter

• retains urine in bladder

• smooth muscle, involuntary

External urethral sphincter

• Provides voluntary control over voiding of urine

• skeletal muscle

Excretion

The removal of organic waste product from body fluids

Elimination

The discharge of waste products into the environment

Glomerular filtration

Creates a plasmalike filtrate of the blood

Tubular reabsorption

Removes useful solutes from the filtrate, returns them to the blood

Tubular secretion

Removes additional wastes from the blood, adds them to the filtrate

Water conservation

Removes water from the urine and returns it to blood, concentrates wastes

muscle

its main characteristic is the ability to contract and shorten, making movements possible

3 types:

1. Skeletal

2. Cardiac

3. Smooth

skeletal muscle

• attaches to the skeleton and enables the body to move

• voluntary muscle

• long, cylindrical, containing several nuclei per cell

• striated (or banded) due to the arrangement of protein in the cell

cardiac muscle

• muscle of the heart

• involuntary control, pumps the blood

• cylindrical cells, shorter than skeletal muscle cells

• striated, 1 nucleus per cell

intercalated discs

gap junctions that link adjacent cardiac muscles so that electrical impulses can travel between cells and causes to contract almost simultaneously

smooth muscle

• forms the walls of hollow organs (except the heart)

• found in the skin and eyes

• moves food through the digestive tract

• empties urinary bladder

• involuntary control

• cell has no striations, single nucleus, and tapered at each end (fusiform)

40%

about __% of the body is made up of skeletal muscle

10%

about __% of the body is made up of cardiac and smooth muscle

10-80

all skeletal muscles are composed of numerous fibers ranging from (?) micrometers in diameter

sarcomeres

a regular pattern of functional units — basic contractile unit of muscle fiber

epimysium

• External sheath of connective tissue surrounding the whole muscle

• separates whole muscles from one another

• covered by fascia

Whole muscle

Made up of multiple muscle fascicles

muscle fascicle

• Bundles of individual muscle fibers

• Surrounded by perimysium:

  • Thin sheaths of connective tissue

  • Continuous with epimysium at their ends

Muscle fibers

• Individual muscle cells (but typically called “fibers” because they are so long)

• Immediately encased by sarcolemma (muscle cell–specific

  cell membrane)

• surrounded by endomysium

  • Thin sheaths of areolar connective tissue

  • Contain capillaries and nerve fibers to supply each cell/fiber

  • Continuous with perimysium and epimysium at their ends

perimysium

• Thin sheaths of connective tissue

• Continuous with epimysium at their ends

sarcolemma

the plasma membrane of the muscle cell

myofibrils

• Long functional subunits made up of myofilaments within a muscle cell

• Surrounded by sarcoplasmic reticulum

• Take up a majority of the sarcoplasm 

myofilaments

individual contractile proteins

sarcoplasm

• Muscle cell cytoplasm

• Primarily filled with protein bundles called myofibrils

myoglobin

binds/stores O2 until needed

glycogen

used for energy

sarcoplasmic reticulum

• Specialized smooth endoplasmic reticulum

• Forms a network around each myofibril

myosin

thick straight filaments arranged in parallel

actin filaments

lighter band (microscopically)

Z-line

tails of actin filament

M-line

middle portion of sarcomere

H-zone

portion between m-line and z-line

Connective tissue

group of tissues in the body that:

• maintain the form of the body and its organs

• provide cohesion and internal support

ground substance

Unstructured material that fills the space between cells and contains all components of the extracellular matrix (ECM)

Collagen fibers

• Consists mostly of cross-linked collagen protein

• Provides high-tensile strength

• Larger fibers consist of small cross-striated fibrils

• The glycine-proline-hydroxyproline sequence is vital for its structure

glycine-proline-hydroxyproline

the amino acid sequence vital for collagen fiber structure

Elastic fibers

• Consists of the rubber-like protein elastin

• Long and thin branching fibers; highly distensible

• Lack structural subunits (fibrils) unlike collagen

• Rich in glycine and proline, but also contain large amounts of valine and the unique amino acid, desmosine

  • found in skin, lungs, blood vessel walls

skin, lungs, blood vessel walls

where are elastic fibers found?

fibroblasts

examples of stationary cells

lymphocytes, macrophages, mast cells

examples of migratory cells

stationary cells

• cells that can be of the mature or immature types

• the undifferentiated (immature) cell type has the suffix "blast":

  • connective tissue proper: fibroblast

  • cartilage: chondroblast

  • bone: osteoblast

fibroblasts

• Major cell type of the prototypical connective tissue

• Long and spindle-shaped cells

• Secrete tropocollagen (a precursor of collagen) and constituents of the ground substance

tropocollagen

what do fibroblasts secrete?

retain water; support and cushion organs

Function of loose areolar connective tissue

loose areolar connective tissue

connective tissue that:

• Support and bind other tissues

• Hold body fluids

• Defend against infections

• Consist of fibroblasts, macrophages, fat cells, and occasional mast cells

• Typical arrangement is that of loose fibers forming “empty spaces”: a

  reservoir of fluid

• High hyaluronic acid content

• Retains water seen in edema

Lipid storage

Function of loose adipose connective tissue

Loose adipose connective tissue

Major function: lipid storage

• Adipocytes are the predominant cell type (90%)

  • can develop anywhere there is areolar tissue

• matrix is rare

• cells are packed close together

• richly vascularized

White adipose tissue

type of adipose tissue that stores energy that is used during periods of fasting

Brown adipose tissue

type of adipose tissue mainly located between the shoulder blades and in the neck and abdominal wall

structural support for liver, spleen, lymph nodes

Function of loose reticular connective tissue

loose reticular connective tissue

• Fine fibers composed of collagen that form fine-meshed networks around cells and help maintain the integrity of organs

• Function: structural support of the liver, spleen, and lymph nodes

• Mostly made up of reticular fibers (type III collagen)

liver, spleen, lymph nodes

where is loose reticular connective tissue found?

Dense connective tissue

Function: support and transmit mechanical forces

Dense regular connective tissue

• Closely packed collagen bundles

• Fibers are arranged in the direction of the pulling forces

• Fibroblasts are arranged between fibers

• Present in tendons, aponeuroses, ligaments

tendons, aponeuroses, ligaments

where is dense regular connective tissue found?

Dense irregular connective tissue

• Collagen bundles are thicker and the arrangement is multidirectional

• Resists pulling forces from multiple directions

• Present in organ capsules, dermis, joint capsules

organ capsules, joint capsules, dermis

Where is dense irregular connective tissue found?

Elastic connective tissue

• Extremely elastic connective tissue proper

• Present in nuchal ligament and ligamentum flavum

Reticular fibers

distinguished by their tendency to form fine-meshed networks around cells and cell groups and by virtue of their property of staining black, because of adsorption of metallic silver, when they are treated with alkaline solutions of reducible silver salts.

Ground substance

a transparent material with the properties of a viscous solution or a highly hydrated thin gel

Fibrocytes

They are stimulated to develop into fibroblasts

Mast cells

Cells that mediate inflammatory responses such as hypersensitivity and allergic reactions.

Macrophages

• aka histiocytes

• derived from circulating monocytes in the bloodstream

• important for tissue repair and defense against bacteria

Synovial membrane

• lines joint capsules

• lubricant and nutrient of avascular joint surfaces

Cartilage

a form of connective tissue in which the ground substance is abundant and of a firmly gelated consistency that endows this tissue with unusual rigidity and resistance to compression.

Chondrocytes

cells of cartilage that are isolated in small lacunae within the matrix

Bone

consists of cells, fibres, and ground substance, but, in addition, the extracellular components are impregnated with minute crystals of calcium phosphate in the form of the mineral hydroxyapatite.

Histiocytes

macrophages are also known as (?)

Simple cuboidal epithelium

• single layer of cube-like cells

• carry out facilitated transport, active transport, or secretion

• ex. kidney tubules that have large portion of walls

• excretes the harmful by-products into the urine

simple cuboidal epithelium

what type of epithelium lines the bronchioles of the lungs?