APC 3- The body systems

all the body systems ,how they work ,blood vessels

Describe the function of the digestive system?

functions of the digestive systems:

• •Functions: Ingestion (taking in food), Mixing (stomach), Secretion (stomach e g. Digestive enzymes  ) , Digestion, Absorption (small intestine), Elimination (Anus)

What doe the digestive system consist of?

-the alimentary GI Tract 9m long

-continuous lumen for an external environment

It has the same 3 layers throughout: Mucosa (epithelial cells lining the mucous glands),Muscle (contracts) and connective tissue (serosa, protects)

-mucous -helps to lubricate as food goes through the system

-the small intestine is not smooth

-squeeze food in different directions

-connective tissue - keeps us warm and protects

What is a GI Tract ?

Gastrointestinal tract - long tube that extends from the mouth to the anus ,transporting food etc ..

Describe the structure of the upper Gi Tract?

Oral cavity:

•Accessory organs: teeth, tongue, salivary glands ( not part of Gi but aid digestion)

•Buccal (between cheeks and teeth)

•Sublingual/Translingual (under/on tongue)

•Mucosa has rich blood supply for absorption

Oesophagus:

•Muscular contractions – controlled by nervous system (peristalsis- squeezing food down to stomach )

•Inferior sphincter prevents stomach reflux

Stomach: Gastric pits-go down to crypts where there are cells that produce substances :  Examples

•HCl: pH2; antimicrobial & denaturing

•Pepsin: hydrolyses peptide bonds in protein

•rich Blood supply – but limited absorption ,helps to prevent break down of drugs 
Duodenum (~25 cm):

Site of bile and pancreatic juice entry to GI tract

Describe the structure of the lower GI Tract?

Jejunum (~2.5m) and Ileum (~3.5m)

•Mucosa adapted - villi and microvilli

•↑ ↑ surface area for absorption of nutrients/drugs* into blood

•*Fats/fat soluble drugs taken up first via lacteals (green) into lymphatic system 

Large intestine (colon): 3 REGIONS 

•Reabsorbs 90% of remaining (1.5L) water/day (dysfunction → diarrhoea)

•Limited absorption for drugs (no villi)

•Rectal route for drug absorption

•Microbiome – where bacteria lives  – modifies (some) drugs 

What is the main function of the liver ?

-produces bile

Where does the liver receive blood from?

Largest internal organ

•Receives blood from:

1. Hepatic artery (branch of aorta)

2. Hepatic portal vein - ( detoxifies blood) from GI tract, spleen, pancreas

•Produces bile  

Describe the Metabolic functions of the liver 

•Glycogenesis (glucose → glycogen)

•Gluconeogenesis (lactate/amino acids → glucose

•Amino acid breakdown

•Clotting factors and albumin synthesis

•First-pass metabolism of most oral drugs*

•*remember fat-soluble drugs absorbed into lacteals – do not end up in h.p.v.

Why does the liver need a constant blood supply?

for respiration to nourish the cells as it is highly metabolic organ

What is the Function of the gall bladder ?

Stores bile made in liver

What does the bile contain ?

Bile:

•Contains bile salts, cholesterol, bilirubin (breakdown  from r.b.c. turnover)

•Essential for fat emulsification (increase sa to form chylomicrons from micelles) and hence absorption of dietary fat, fat-soluble drugs and vitamins (A, D, E, K)

•Released via common bile duct into duodenum along with  pancreatic juices

What is the Exocrine function of the pancreas?

Exocrine

• releases Pancreatic juice: containing  Amylase, lipase, protease from acinar cells, and bicarbonate (neutralises* stomach acid)

•Released via pancreatic duct into duodenum

What is the endocrine function of the pancrease?

Endocrine

• reaeases Hormones: into bloodstream

•Insulin when blood glucose is ↑

•Glucagon when blood glucose is ↓

NOTE- *pH important for drug absorption

Structure of gall bladder and pancreas

What is the main function of the cardiovascular system ?

•: distribution (mass transport) of O₂/CO₂, nutrients, hormones, heat, clotting factors, drugs

What does the distribution rate depend on ?

cardiac output (CO): amount of blood pumped out of the heart in one minute

•1 min for blood to move round the whole system:

      Aorta → systemic circulation → right heart → lungs →  
      left heart → Aorta

Describe the structure of the heart ?

4 chambers: R/L side separated by septum:

Right atrium (RA)

Right ventricle (RV)

Left atrium (LA)

Left Ventricle (LV)

4 valves prevent backflow:

Tricuspid- prevent right v to r a 

Pulmonary semilunar prevent blood back form left v

Bicuspid (mitral)

Aortic semilunar

Coronary arteries branch off aorta – supply blood to heart tissue

Sinoatrial node initiates impulse for contraction

What is the the direction of blood flow in the heart ?

Direction of blood flow:

Body → RA → RV → Lungs → LA → LV → Body

What does blood consists of ?

Blood

Transport for O₂, CO₂, nutrients, hormones, drugs

Components: plasma (water, proteins, clotting factors, ions), red & white blood cells, platelets (thrombocytes)

What are the main Blood vessels ?

Blood Vessels – all lined by endothelial cells

•Arteries – thick muscular walls, blood under high pressure away from heart

•Arterioles - smaller arteries - muscular wall can constrict to increase blood pressure  - how brain controls blood p ,and  vasodilation …

•Veins – thinner muscle layer, valves prevent back flow, blood under low pressure back to heart

•Capillaries – thin walled (single layer of cells) fairly permeable, site of exchange (nutrients, gases, drugs),no muscular layer

What is tissue perfusion?

●the process of blood flowing through the blood vessels to deliver oxygen and nutrients to cells and remove carbon dioxide and waste products, can use oximeter

●Oxygen and substance are transported through water acts as a transport medium

●Osmotic p,< capillary p

●Gives extra fluid

Which is transported in lymph vessels

NOTE- Distribution rate will affect he amount of tissue perfusion( for nutrient ,gas, drugs)

What is the function of the lymphatic system?

Functions:

○Drains excess tissue fluid from tissues after capillary exchange and returns it to blood

○Absorb fats and fat/soluble drugs in chylomicrons (via lacteals)

○Immune system: circulation & activation of lymphocytes (type of WBC)

What is lymph and where does it go?

Fluid = lymph (similar to plasma, fewer proteins)

Enters the blood circulation via thoracic duct  - left    or right goes to  right lymphatic duct

NOTE- ONLY GOE SIN ONE DIRECTION ALL TOWARDS THE HEART 

Describe the structure of the respiratory tract?

Upper tract:

Nose, pharynx, larynx:  filters, warms, humidifies air

Lower tract: trachea, bronchi, bronchioles, alveoli: conduct & exchange gases

Lining: ciliated epithelium and goblet cells (mucus + ciliary clearance)

Inhaled irritants/drugs can affect mucociliary clearance (e.g. smoking)

Where does gas exchange occur ?

•Occurs in alveoli (tiny air sacs, 300 million in lungs)

Thin respiratory membrane (alveolar epithelium and capillary endothelium

How does gas exchange occur ?

•Gases move by simple diffusion (from area of higher concentration to area of lower concentration

•O₂:from alveoli → blood

•CO₂: from blood → alveoli

•Inhaled drugs can reach the blood quickly

•Lungs also excrete volatile drugs e.g., anaesthetics, alcohol

NOTE- higher concentration of o2 in alveoli  so it can diffuse into the blood 

What are the functions of the renal system 

•Filter blood to remove waste (urea, creatinine, drugs)

•Major site of drug excretion

•Maintain water & electrolyte balance (Na⁺, K⁺, Ca²⁺, Cl⁻)

•Regulate pH of blood (H⁺ secretion into blood, HCO₃⁻ reabsorption from blood)

•Control blood pressure (RAAS system)

•Produce the erythropoietin hormone - stimulates RBC production in bone marrow

•Location of final stage of vitamin D activation in calcitriol 

What is the structure of the renal system ?

Organs- 2 kidneys,2 ureters ,bladder and urethra

What is the Nephron?

Functional unit of a kidney -filter blood, remove waste products like urea, and regulate the balance of water, electrolytes, and acids in the body to form urine

Decribe the key structures and their roles in the nephron?

•Glomerulus and Bowman’s capsule: site of blood filtration, forms filtrate in nephron

•Proximal convoluted tubule (PCT): reabsorbs most Na⁺, water, glucose, amino acids

•Loop of Henle: concentrates urine (descending limb: water out, ascending limb: Na⁺ out)

•Distal tubule and Collecting duct:  controls final Na⁺, K⁺, water in urine; regulated by Antidiuretic hormone (ADH) from posterior pituitary gland and Aldosterone from the cortex (outer region) of adrenal gland 

•Nephron = site of action of diuretics - decrease amount of water reabsorbed into blood: increase water output in urine

•Excretion = filtration – reabsorption + secretion

NOTE - DIURETIC DRUGS - prevent uptake of ions  

What is the function of the nervous system ?

Main functions: control, coordination, communication within the body

What are the 2 major divisions?

MAJOR DIVISIONS 

•Central Nervous System (CNS) – brain and spinal cord (integration, processing, higher functions)
•Peripheral Nervous System (PNS) – cranial & spinal nerves (connect CNS ↔ body)

SUBDIVISIONS PNS:

•Somatic – voluntary, skeletal muscle control

•Autonomic (ANS) – involuntary, smooth muscle, glands, heart

•Sympathetic: fight or flight

•Parasympathetic: rest and digest